diff --git a/eslint-suppressions.json b/eslint-suppressions.json
index 4646a9b2a21..b7493f59e9a 100644
--- a/eslint-suppressions.json
+++ b/eslint-suppressions.json
@@ -1560,33 +1560,6 @@
       "count": 3
     }
   },
-  "packages/notification-services-controller/src/NotificationServicesController/NotificationServicesController.test.ts": {
-    "@typescript-eslint/explicit-function-return-type": {
-      "count": 23
-    },
-    "id-length": {
-      "count": 7
-    }
-  },
-  "packages/notification-services-controller/src/NotificationServicesController/NotificationServicesController.ts": {
-    "@typescript-eslint/explicit-function-return-type": {
-      "count": 31
-    },
-    "@typescript-eslint/no-misused-promises": {
-      "count": 1
-    },
-    "id-denylist": {
-      "count": 5
-    },
-    "id-length": {
-      "count": 8
-    }
-  },
-  "packages/notification-services-controller/src/NotificationServicesController/__fixtures__/mockServices.ts": {
-    "@typescript-eslint/explicit-function-return-type": {
-      "count": 6
-    }
-  },
   "packages/notification-services-controller/src/NotificationServicesController/constants/notification-schema.ts": {
     "@typescript-eslint/naming-convention": {
       "count": 18
diff --git a/packages/notification-services-controller/src/NotificationServicesController/NotificationServicesController.test.ts b/packages/notification-services-controller/src/NotificationServicesController/NotificationServicesController.test.ts
index 1870ac086d8..01620f2c603 100644
--- a/packages/notification-services-controller/src/NotificationServicesController/NotificationServicesController.test.ts
+++ b/packages/notification-services-controller/src/NotificationServicesController/NotificationServicesController.test.ts
@@ -61,12 +61,13 @@ const featureAnnouncementsEnv = {
 };
 
 // Testing util to clean up verbose logs when testing errors
-const mockErrorLog = () =>
+const mockErrorLog = (): jest.SpyInstance =>
   jest.spyOn(log, 'error').mockImplementation(jest.fn());
-const mockWarnLog = () => jest.spyOn(log, 'warn').mockImplementation(jest.fn());
+const mockWarnLog = (): jest.SpyInstance =>
+  jest.spyOn(log, 'warn').mockImplementation(jest.fn());
 
 // Removing caches to avoid interference
-const clearAPICache = () => {
+const clearAPICache = (): void => {
   notificationsConfigCache.clear();
 };
 
@@ -94,11 +95,11 @@ describe('NotificationServicesController', () => {
   });
 
   describe('init', () => {
-    const arrangeMocks = () => {
+    const arrangeMocks = (): ReturnType<typeof mockNotificationMessenger> => {
       const messengerMocks = mockNotificationMessenger();
       jest
         .spyOn(ControllerUtils, 'toChecksumHexAddress')
-        .mockImplementation((x) => x);
+        .mockImplementation((address) => address);
 
       return messengerMocks;
     };
@@ -107,7 +108,7 @@ describe('NotificationServicesController', () => {
       // eslint-disable-next-line @typescript-eslint/no-explicit-any
       messenger: any,
       accounts: string[] = ['0x111', '0x222'],
-    ) => {
+    ): Promise<void> => {
       messenger.publish(
         'KeyringController:stateChange',
         {
@@ -119,7 +120,11 @@ describe('NotificationServicesController', () => {
 
     const arrangeActAssertKeyringTest = async (
       controllerState?: Partial<NotificationServicesControllerState>,
-    ) => {
+    ): Promise<{
+      act: (addresses: string[], assertion: () => void) => Promise<void>;
+      mockEnable: jest.SpyInstance;
+      mockDisable: jest.SpyInstance;
+    }> => {
       const mocks = arrangeMocks();
       const { messenger, globalMessenger, mockKeyringControllerGetState } =
         mocks;
@@ -155,7 +160,10 @@ describe('NotificationServicesController', () => {
         .spyOn(controller, 'disableAccounts')
         .mockResolvedValue();
 
-      const act = async (addresses: string[], assertion: () => void) => {
+      const act = async (
+        addresses: string[],
+        assertion: () => void,
+      ): Promise<void> => {
         mockKeyringControllerGetState.mockReturnValue({
           isUnlocked: true,
           keyrings: [
@@ -246,7 +254,9 @@ describe('NotificationServicesController', () => {
 
     const arrangeActInitialisePushNotifications = (
       modifications?: (mocks: ReturnType<typeof arrangeMocks>) => void,
-    ) => {
+    ): ReturnType<typeof arrangeMocks> & {
+      mockAPIGetNotificationConfig: nock.Scope;
+    } => {
       // Arrange
       const mockAPIGetNotificationConfig = mockGetOnChainNotificationsConfig();
       const mocks = arrangeMocks();
@@ -378,7 +388,12 @@ describe('NotificationServicesController', () => {
   });
 
   describe('createOnChainTriggers', () => {
-    const arrangeMocks = (overrides?: { mockGetConfig: () => nock.Scope }) => {
+    const arrangeMocks = (overrides?: {
+      mockGetConfig: () => nock.Scope;
+    }): ReturnType<typeof mockNotificationMessenger> & {
+      mockGetConfig: nock.Scope;
+      mockUpdateNotifications: nock.Scope;
+    } => {
       const messengerMocks = mockNotificationMessenger();
       const mockGetConfig =
         overrides?.mockGetConfig() ?? mockGetOnChainNotificationsConfig();
@@ -532,7 +547,9 @@ describe('NotificationServicesController', () => {
   });
 
   describe('disableAccounts', () => {
-    const arrangeMocks = () => {
+    const arrangeMocks = (): ReturnType<typeof mockNotificationMessenger> & {
+      mockUpdateNotifications: nock.Scope;
+    } => {
       const messengerMocks = mockNotificationMessenger();
       const mockUpdateNotifications = mockUpdateOnChainNotifications();
       return { ...messengerMocks, mockUpdateNotifications };
@@ -572,7 +589,9 @@ describe('NotificationServicesController', () => {
   });
 
   describe('enableAccounts', () => {
-    const arrangeMocks = () => {
+    const arrangeMocks = (): ReturnType<typeof mockNotificationMessenger> & {
+      mockUpdateNotifications: nock.Scope;
+    } => {
       const messengerMocks = mockNotificationMessenger();
       const mockUpdateNotifications = mockUpdateOnChainNotifications();
       return { ...messengerMocks, mockUpdateNotifications };
@@ -612,7 +631,17 @@ describe('NotificationServicesController', () => {
   });
 
   describe('fetchAndUpdateMetamaskNotifications', () => {
-    const arrangeMocks = () => {
+    const arrangeMocks = (): ReturnType<typeof mockNotificationMessenger> & {
+      mockNotificationConfigAPI: nock.Scope;
+      mockFeatureAnnouncementAPIResult: ReturnType<
+        typeof createMockFeatureAnnouncementAPIResult
+      >;
+      mockFeatureAnnouncementsAPI: nock.Scope;
+      mockOnChainNotificationsAPIResult: ReturnType<
+        typeof createMockNotificationEthSent
+      >[];
+      mockOnChainNotificationsAPI: nock.Scope;
+    } => {
       const messengerMocks = mockNotificationMessenger();
 
       const mockFeatureAnnouncementAPIResult =
@@ -646,7 +675,7 @@ describe('NotificationServicesController', () => {
     const arrangeController = (
       messenger: NotificationServicesControllerMessenger,
       overrideState?: Partial<NotificationServicesControllerState>,
-    ) => {
+    ): NotificationServicesController => {
       const controller = new NotificationServicesController({
         messenger,
         env: { featureAnnouncements: featureAnnouncementsEnv },
@@ -677,18 +706,25 @@ describe('NotificationServicesController', () => {
 
       // Should have 1 feature announcement
       expect(
-        result.filter((n) => n.type === TRIGGER_TYPES.FEATURES_ANNOUNCEMENT),
+        result.filter(
+          (notification) =>
+            notification.type === TRIGGER_TYPES.FEATURES_ANNOUNCEMENT,
+        ),
       ).toHaveLength(1);
 
       // Should have 1 Wallet Notification
       expect(
-        result.filter((n) => n.type === TRIGGER_TYPES.ETH_SENT),
+        result.filter(
+          (notification) => notification.type === TRIGGER_TYPES.ETH_SENT,
+        ),
       ).toHaveLength(1);
 
       // Should have 1 Snap Notification
-      expect(result.filter((n) => n.type === TRIGGER_TYPES.SNAP)).toHaveLength(
-        1,
-      );
+      expect(
+        result.filter(
+          (notification) => notification.type === TRIGGER_TYPES.SNAP,
+        ),
+      ).toHaveLength(1);
 
       // Total notification length = 3
       expect(result).toHaveLength(3);
@@ -708,9 +744,11 @@ describe('NotificationServicesController', () => {
       // Should only contain snap notification
       // As this is not controlled by the global notification switch
       expect(result).toHaveLength(1);
-      expect(result.filter((n) => n.type === TRIGGER_TYPES.SNAP)).toHaveLength(
-        1,
-      );
+      expect(
+        result.filter(
+          (notification) => notification.type === TRIGGER_TYPES.SNAP,
+        ),
+      ).toHaveLength(1);
 
       // APIs should not have been called
       expect(mocks.mockFeatureAnnouncementsAPI.isDone()).toBe(false);
@@ -727,7 +765,10 @@ describe('NotificationServicesController', () => {
 
       // Should not have any feature announcements
       expect(
-        result.filter((n) => n.type === TRIGGER_TYPES.FEATURES_ANNOUNCEMENT),
+        result.filter(
+          (notification) =>
+            notification.type === TRIGGER_TYPES.FEATURES_ANNOUNCEMENT,
+        ),
       ).toHaveLength(0);
 
       // Should not have called feature announcement API
@@ -895,7 +936,11 @@ describe('NotificationServicesController', () => {
   });
 
   describe('markMetamaskNotificationsAsRead', () => {
-    const arrangeMocks = (options?: { onChainMarkAsReadFails: boolean }) => {
+    const arrangeMocks = (options?: {
+      onChainMarkAsReadFails: boolean;
+    }): ReturnType<typeof mockNotificationMessenger> & {
+      mockMarkAsReadAPI: nock.Scope;
+    } => {
       const messengerMocks = mockNotificationMessenger();
 
       const mockMarkAsReadAPI = mockMarkNotificationsAsRead({
@@ -977,7 +1022,12 @@ describe('NotificationServicesController', () => {
   });
 
   describe('enableMetamaskNotifications', () => {
-    const arrangeMocks = (overrides?: { mockGetConfig: () => nock.Scope }) => {
+    const arrangeMocks = (overrides?: {
+      mockGetConfig: () => nock.Scope;
+    }): ReturnType<typeof mockNotificationMessenger> & {
+      mockGetConfig: nock.Scope;
+      mockUpdateNotifications: nock.Scope;
+    } => {
       const messengerMocks = mockNotificationMessenger();
       const mockGetConfig =
         overrides?.mockGetConfig() ?? mockGetOnChainNotificationsConfig();
@@ -1143,7 +1193,9 @@ describe('NotificationServicesController', () => {
   });
 
   describe('enablePushNotifications', () => {
-    const arrangeMocks = () => {
+    const arrangeMocks = (): ReturnType<typeof mockNotificationMessenger> & {
+      mockGetConfig: nock.Scope;
+    } => {
       const messengerMocks = mockNotificationMessenger();
       const mockGetConfig = mockGetOnChainNotificationsConfig({
         status: 200,
@@ -1214,7 +1266,9 @@ describe('NotificationServicesController', () => {
   });
 
   describe('sendPerpPlaceOrderNotification', () => {
-    const arrangeMocks = () => {
+    const arrangeMocks = (): ReturnType<typeof mockNotificationMessenger> & {
+      mockCreatePerpAPI: nock.Scope;
+    } => {
       const messengerMocks = mockNotificationMessenger();
       const mockCreatePerpAPI = mockCreatePerpNotification({
         status: 200,
@@ -1396,8 +1450,10 @@ describe('NotificationServicesController', () => {
 // Thus this `AnyFunc` can be used to help constrain the generic parameters correctly
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
 type AnyFunc = (...args: any[]) => any;
-const typedMockAction = <Action extends { handler: AnyFunc }>() =>
-  jest.fn<ReturnType<Action['handler']>, Parameters<Action['handler']>>();
+const typedMockAction = <Action extends { handler: AnyFunc }>(): jest.Mock<
+  ReturnType<Action['handler']>,
+  Parameters<Action['handler']>
+> => jest.fn<ReturnType<Action['handler']>, Parameters<Action['handler']>>();
 
 const controllerName = 'NotificationServicesController';
 
@@ -1429,7 +1485,17 @@ function getRootMessenger(): RootMessenger {
  *
  * @returns mock notification messenger and other messenger mocks
  */
-function mockNotificationMessenger() {
+function mockNotificationMessenger(): {
+  globalMessenger: RootMessenger;
+  messenger: NotificationServicesControllerMessenger;
+  mockGetBearerToken: jest.Mock;
+  mockIsSignedIn: jest.Mock;
+  mockAuthPerformSignIn: jest.Mock;
+  mockDisablePushNotifications: jest.Mock;
+  mockEnablePushNotifications: jest.Mock;
+  mockSubscribeToPushNotifications: jest.Mock;
+  mockKeyringControllerGetState: jest.Mock;
+} {
   const globalMessenger = getRootMessenger();
 
   const messenger = new Messenger<
@@ -1568,15 +1634,19 @@ function mockNotificationMessenger() {
  */
 function arrangeFailureAuthAssertions(
   mocks: ReturnType<typeof mockNotificationMessenger>,
-) {
+): {
+  notLoggedIn: () => jest.Mock;
+  noBearerToken: () => jest.Mock;
+  rejectedBearerToken: () => jest.Mock;
+} {
   const testScenarios = {
-    NotLoggedIn: () => mocks.mockIsSignedIn.mockReturnValue(false),
+    notLoggedIn: (): jest.Mock => mocks.mockIsSignedIn.mockReturnValue(false),
 
     // unlikely, but in case it returns null
-    NoBearerToken: () =>
+    noBearerToken: (): jest.Mock =>
       mocks.mockGetBearerToken.mockResolvedValueOnce(null as unknown as string),
 
-    RejectedBearerToken: () =>
+    rejectedBearerToken: (): jest.Mock =>
       mocks.mockGetBearerToken.mockRejectedValueOnce(
         new Error('MOCK - no bearer token'),
       ),
diff --git a/packages/notification-services-controller/src/NotificationServicesController/NotificationServicesController.ts b/packages/notification-services-controller/src/NotificationServicesController/NotificationServicesController.ts
index ed8ad1a41e5..80659ed91f9 100644
--- a/packages/notification-services-controller/src/NotificationServicesController/NotificationServicesController.ts
+++ b/packages/notification-services-controller/src/NotificationServicesController/NotificationServicesController.ts
@@ -291,11 +291,11 @@ export default class NotificationServicesController extends BaseController<
   readonly #keyringController = {
     isUnlocked: false,
 
-    setupLockedStateSubscriptions: (onUnlock: () => Promise<void>) => {
+    setupLockedStateSubscriptions: (onUnlock: () => Promise<void>): void => {
       const { isUnlocked } = this.messenger.call('KeyringController:getState');
       this.#keyringController.isUnlocked = isUnlocked;
 
-      this.messenger.subscribe('KeyringController:unlock', () => {
+      this.messenger.subscribe('KeyringController:unlock', (): void => {
         this.#keyringController.isUnlocked = true;
         // messaging system cannot await promises
         // we don't need to wait for a result on this.
@@ -303,22 +303,22 @@ export default class NotificationServicesController extends BaseController<
         onUnlock();
       });
 
-      this.messenger.subscribe('KeyringController:lock', () => {
+      this.messenger.subscribe('KeyringController:lock', (): void => {
         this.#keyringController.isUnlocked = false;
       });
     },
   };
 
   readonly #auth = {
-    getBearerToken: async () => {
+    getBearerToken: async (): Promise<string | null> => {
       return await this.messenger.call(
         'AuthenticationController:getBearerToken',
       );
     },
-    isSignedIn: () => {
+    isSignedIn: (): boolean => {
       return this.messenger.call('AuthenticationController:isSignedIn');
     },
-    signIn: async () => {
+    signIn: async (): Promise<string[]> => {
       return await this.messenger.call(
         'AuthenticationController:performSignIn',
       );
@@ -331,40 +331,40 @@ export default class NotificationServicesController extends BaseController<
     // To ensure we subscribe to the most up-to-date notifications
     isSetup: false,
 
-    subscribeToPushNotifications: async () => {
+    subscribeToPushNotifications: async (): Promise<void> => {
       await this.messenger.call(
         'NotificationServicesPushController:subscribeToPushNotifications',
       );
     },
-    enablePushNotifications: async (addresses: string[]) => {
+    enablePushNotifications: async (addresses: string[]): Promise<void> => {
       try {
         await this.messenger.call(
           'NotificationServicesPushController:enablePushNotifications',
           addresses,
         );
-      } catch (e) {
-        log.error('Silently failed to enable push notifications', e);
+      } catch (error) {
+        log.error('Silently failed to enable push notifications', error);
       }
     },
-    disablePushNotifications: async () => {
+    disablePushNotifications: async (): Promise<void> => {
       try {
         await this.messenger.call(
           'NotificationServicesPushController:disablePushNotifications',
         );
-      } catch (e) {
-        log.error('Silently failed to disable push notifications', e);
+      } catch (error) {
+        log.error('Silently failed to disable push notifications', error);
       }
     },
-    subscribe: () => {
+    subscribe: (): void => {
       this.messenger.subscribe(
         'NotificationServicesPushController:onNewNotifications',
-        (notification) => {
+        (notification): void => {
           // eslint-disable-next-line @typescript-eslint/no-floating-promises
           this.updateMetamaskNotificationsList(notification);
         },
       );
     },
-    initializePushNotifications: async () => {
+    initializePushNotifications: async (): Promise<void> => {
       if (!this.state.isNotificationServicesEnabled) {
         return;
       }
@@ -394,10 +394,10 @@ export default class NotificationServicesController extends BaseController<
     // Flag to ensure we only setup once
     isNotificationAccountsSetup: false,
 
-    getNotificationAccounts: () => {
+    getNotificationAccounts: (): string[] | null => {
       const { keyrings } = this.messenger.call('KeyringController:getState');
       const firstHDKeyring = keyrings.find(
-        (k) => k.type === KeyringTypes.hd.toString(),
+        (keyring) => keyring.type === KeyringTypes.hd.toString(),
       );
       const keyringAccounts = firstHDKeyring?.accounts ?? null;
       return keyringAccounts;
@@ -408,7 +408,11 @@ export default class NotificationServicesController extends BaseController<
      *
      * @returns addresses removed, added, and latest list of addresses
      */
-    listAccounts: () => {
+    listAccounts: (): {
+      accountsAdded: string[];
+      accountsRemoved: string[];
+      accounts: string[];
+    } => {
       // Get previous and current account sets
       const nonChecksumAccounts = this.#accounts.getNotificationAccounts();
       if (!nonChecksumAccounts) {
@@ -420,8 +424,8 @@ export default class NotificationServicesController extends BaseController<
       }
 
       const accounts = nonChecksumAccounts
-        .map((a) => toChecksumHexAddress(a))
-        .filter((a) => isValidHexAddress(a));
+        .map((address) => toChecksumHexAddress(address))
+        .filter((address) => isValidHexAddress(address));
       const currentAccountsSet = new Set(accounts);
       const prevAccountsSet = new Set(this.state.subscriptionAccountsSeen);
 
@@ -436,9 +440,11 @@ export default class NotificationServicesController extends BaseController<
       }
 
       // Calculate added and removed addresses
-      const accountsAdded = accounts.filter((a) => !prevAccountsSet.has(a));
+      const accountsAdded = accounts.filter(
+        (account) => !prevAccountsSet.has(account),
+      );
       const accountsRemoved = [...prevAccountsSet.values()].filter(
-        (a) => !currentAccountsSet.has(a),
+        (account) => !currentAccountsSet.has(account),
       );
 
       // Update accounts seen
@@ -471,11 +477,12 @@ export default class NotificationServicesController extends BaseController<
      * We can call the `listAccounts` defined above to find out about any accounts added, removed
      * And call effects to subscribe/unsubscribe to notifications.
      */
-    subscribe: () => {
+    subscribe: (): void => {
       this.messenger.subscribe(
         'KeyringController:stateChange',
-
-        async (totalAccounts, prevTotalAccounts) => {
+        // Using void return for async callback - result is intentionally ignored
+        // eslint-disable-next-line @typescript-eslint/no-misused-promises
+        async (totalAccounts, prevTotalAccounts): Promise<void> => {
           const hasTotalAccountsChanged = totalAccounts !== prevTotalAccounts;
           if (
             !this.state.isNotificationServicesEnabled ||
@@ -544,17 +551,19 @@ export default class NotificationServicesController extends BaseController<
     });
 
     this.#featureAnnouncementEnv = env.featureAnnouncements;
-    this.#locale = env.locale ?? (() => 'en');
+    this.#locale = env.locale ?? ((): string => 'en');
     this.#env = env.env ?? 'prd';
     this.#registerMessageHandlers();
     this.#clearLoadingStates();
   }
 
-  init() {
-    this.#keyringController.setupLockedStateSubscriptions(async () => {
-      this.#accounts.initialize();
-      await this.#pushNotifications.initializePushNotifications();
-    });
+  init(): void {
+    this.#keyringController.setupLockedStateSubscriptions(
+      async (): Promise<void> => {
+        this.#accounts.initialize();
+        await this.#pushNotifications.initializePushNotifications();
+      },
+    );
 
     this.#accounts.initialize();
     // eslint-disable-next-line @typescript-eslint/no-floating-promises
@@ -594,7 +603,7 @@ export default class NotificationServicesController extends BaseController<
     });
   }
 
-  #assertAuthEnabled() {
+  #assertAuthEnabled(): void {
     if (!this.#auth.isSignedIn()) {
       this.update((state) => {
         state.isNotificationServicesEnabled = false;
@@ -603,14 +612,14 @@ export default class NotificationServicesController extends BaseController<
     }
   }
 
-  async #enableAuth() {
+  async #enableAuth(): Promise<void> {
     const isSignedIn = this.#auth.isSignedIn();
     if (!isSignedIn) {
       await this.#auth.signIn();
     }
   }
 
-  async #getBearerToken() {
+  async #getBearerToken(): Promise<{ bearerToken: string }> {
     this.#assertAuthEnabled();
 
     const bearerToken = await this.#auth.getBearerToken();
@@ -634,7 +643,7 @@ export default class NotificationServicesController extends BaseController<
    */
   #setIsUpdatingMetamaskNotifications(
     isUpdatingMetamaskNotifications: boolean,
-  ) {
+  ): void {
     this.update((state) => {
       state.isUpdatingMetamaskNotifications = isUpdatingMetamaskNotifications;
     });
@@ -650,7 +659,7 @@ export default class NotificationServicesController extends BaseController<
    */
   #setIsFetchingMetamaskNotifications(
     isFetchingMetamaskNotifications: boolean,
-  ) {
+  ): void {
     this.update((state) => {
       state.isFetchingMetamaskNotifications = isFetchingMetamaskNotifications;
     });
@@ -665,7 +674,7 @@ export default class NotificationServicesController extends BaseController<
    *
    * @param isCheckingAccountsPresence - A boolean value indicating whether the account presence check is currently active.
    */
-  #setIsCheckingAccountsPresence(isCheckingAccountsPresence: boolean) {
+  #setIsCheckingAccountsPresence(isCheckingAccountsPresence: boolean): void {
     this.update((state) => {
       state.isCheckingAccountsPresence = isCheckingAccountsPresence;
     });
@@ -677,7 +686,7 @@ export default class NotificationServicesController extends BaseController<
    *
    * @param accounts - The accounts being updated.
    */
-  #updateUpdatingAccountsState(accounts: string[]) {
+  #updateUpdatingAccountsState(accounts: string[]): void {
     this.update((state) => {
       const uniqueAccounts = new Set([
         ...state.isUpdatingMetamaskNotificationsAccount,
@@ -692,7 +701,7 @@ export default class NotificationServicesController extends BaseController<
    *
    * @param accounts - The accounts that have finished updating.
    */
-  #clearUpdatingAccountsState(accounts: string[]) {
+  #clearUpdatingAccountsState(accounts: string[]): void {
     this.update((state) => {
       state.isUpdatingMetamaskNotificationsAccount =
         state.isUpdatingMetamaskNotificationsAccount.filter(
@@ -704,7 +713,7 @@ export default class NotificationServicesController extends BaseController<
   /**
    * Public method to expose enabling push notifications
    */
-  public async enablePushNotifications() {
+  public async enablePushNotifications(): Promise<void> {
     try {
       const { bearerToken } = await this.#getBearerToken();
       const { accounts } = this.#accounts.listAccounts();
@@ -714,20 +723,20 @@ export default class NotificationServicesController extends BaseController<
         this.#env,
       );
       const addresses = addressesWithNotifications
-        .filter((a) => Boolean(a.enabled))
-        .map((a) => a.address);
+        .filter((addressConfig) => Boolean(addressConfig.enabled))
+        .map((addressConfig) => addressConfig.address);
       if (addresses.length > 0) {
         await this.#pushNotifications.enablePushNotifications(addresses);
       }
-    } catch (e) {
-      log.error('Failed to enable push notifications', e);
+    } catch (error) {
+      log.error('Failed to enable push notifications', error);
     }
   }
 
   /**
    * Public method to expose disabling push notifications
    */
-  public async disablePushNotifications() {
+  public async disablePushNotifications(): Promise<void> {
     await this.#pushNotifications.disablePushNotifications();
   }
 
@@ -769,13 +778,13 @@ export default class NotificationServicesController extends BaseController<
    */
   public async setFeatureAnnouncementsEnabled(
     featureAnnouncementsEnabled: boolean,
-  ) {
+  ): Promise<void> {
     try {
-      this.update((s) => {
-        s.isFeatureAnnouncementsEnabled = featureAnnouncementsEnabled;
+      this.update((state) => {
+        state.isFeatureAnnouncementsEnabled = featureAnnouncementsEnabled;
       });
-    } catch (e) {
-      log.error('Unable to toggle feature announcements', e);
+    } catch (error) {
+      log.error('Unable to toggle feature announcements', error);
       throw new Error('Unable to toggle feature announcements');
     }
   }
@@ -811,8 +820,8 @@ export default class NotificationServicesController extends BaseController<
       // Notifications API can return array with addresses set to false
       // So assert that at least one address is enabled
       let accountsWithNotifications = addressesWithNotifications
-        .filter((a) => Boolean(a.enabled))
-        .map((a) => a.address);
+        .filter((addressConfig) => Boolean(addressConfig.enabled))
+        .map((addressConfig) => addressConfig.address);
 
       // 2. Enable Notifications (if no accounts subscribed or we are resetting)
       if (accountsWithNotifications.length === 0 || opts?.resetNotifications) {
@@ -844,8 +853,8 @@ export default class NotificationServicesController extends BaseController<
           state.isMetamaskNotificationsFeatureSeen = true;
         }
       });
-    } catch (err) {
-      log.error('Failed to create On Chain triggers', err);
+    } catch (error) {
+      log.error('Failed to create On Chain triggers', error);
       throw new Error('Failed to create On Chain triggers');
     } finally {
       this.#setIsUpdatingMetamaskNotifications(false);
@@ -858,13 +867,13 @@ export default class NotificationServicesController extends BaseController<
    *
    * @throws {Error} If there is an error during the process of enabling notifications.
    */
-  public async enableMetamaskNotifications() {
+  public async enableMetamaskNotifications(): Promise<void> {
     try {
       this.#setIsUpdatingMetamaskNotifications(true);
       await this.#enableAuth();
       await this.createOnChainTriggers();
-    } catch (e) {
-      log.error('Unable to enable notifications', e);
+    } catch (error) {
+      log.error('Unable to enable notifications', error);
       throw new Error('Unable to enable notifications');
     } finally {
       this.#setIsUpdatingMetamaskNotifications(false);
@@ -879,7 +888,7 @@ export default class NotificationServicesController extends BaseController<
    *
    * @throws {Error} If the user is not authenticated or if there is an error during the process.
    */
-  public async disableNotificationServices() {
+  public async disableNotificationServices(): Promise<void> {
     this.#setIsUpdatingMetamaskNotifications(true);
 
     // Attempt Disable Push Notifications
@@ -930,8 +939,8 @@ export default class NotificationServicesController extends BaseController<
         accounts.map((address) => ({ address, enabled: false })),
         this.#env,
       );
-    } catch (err) {
-      log.error('Failed to delete OnChain triggers', err);
+    } catch (error) {
+      log.error('Failed to delete OnChain triggers', error);
       throw new Error('Failed to delete OnChain triggers');
     } finally {
       this.#clearUpdatingAccountsState(accounts);
@@ -963,8 +972,8 @@ export default class NotificationServicesController extends BaseController<
         accounts.map((address) => ({ address, enabled: true })),
         this.#env,
       );
-    } catch (err) {
-      log.error('Failed to update OnChain triggers', err);
+    } catch (error) {
+      log.error('Failed to update OnChain triggers', error);
       throw new Error('Failed to update OnChain triggers');
     } finally {
       this.#clearUpdatingAccountsState(accounts);
@@ -1013,8 +1022,8 @@ export default class NotificationServicesController extends BaseController<
               this.#env,
             )
           )
-            .filter((a) => Boolean(a.enabled))
-            .map((a) => a.address);
+            .filter((addressConfig) => Boolean(addressConfig.enabled))
+            .map((addressConfig) => addressConfig.address);
           const notifications = await getAPINotifications(
             bearerToken,
             addressesWithNotifications,
@@ -1045,8 +1054,9 @@ export default class NotificationServicesController extends BaseController<
 
       // Sort Notifications
       metamaskNotifications.sort(
-        (a, b) =>
-          new Date(b.createdAt).getTime() - new Date(a.createdAt).getTime(),
+        (notificationA, notificationB) =>
+          new Date(notificationB.createdAt).getTime() -
+          new Date(notificationA.createdAt).getTime(),
       );
 
       // Update State
@@ -1061,9 +1071,9 @@ export default class NotificationServicesController extends BaseController<
 
       this.#setIsFetchingMetamaskNotifications(false);
       return metamaskNotifications;
-    } catch (err) {
+    } catch (error) {
       this.#setIsFetchingMetamaskNotifications(false);
-      log.error('Failed to fetch notifications', err);
+      log.error('Failed to fetch notifications', error);
       throw new Error('Failed to fetch notifications');
     }
   }
@@ -1075,7 +1085,7 @@ export default class NotificationServicesController extends BaseController<
    * @returns An array of notifications of the passed in type.
    * @throws Throws an error if an invalid trigger type is passed.
    */
-  public getNotificationsByType(type: TRIGGER_TYPES) {
+  public getNotificationsByType(type: TRIGGER_TYPES): INotification[] {
     assert(
       Object.values(TRIGGER_TYPES).includes(type),
       'Invalid trigger type.',
@@ -1093,7 +1103,7 @@ export default class NotificationServicesController extends BaseController<
    *
    * @param id - The id of the notification to delete.
    */
-  public async deleteNotificationById(id: string) {
+  public async deleteNotificationById(id: string): Promise<void> {
     const fetchedNotification = this.state.metamaskNotificationsList.find(
       (notification) => notification.id === id,
     );
@@ -1130,7 +1140,7 @@ export default class NotificationServicesController extends BaseController<
    *
    * @param ids - The ids of the notifications to delete.
    */
-  public async deleteNotificationsById(ids: string[]) {
+  public async deleteNotificationsById(ids: string[]): Promise<void> {
     for (const id of ids) {
       await this.deleteNotificationById(id);
     }
@@ -1216,8 +1226,8 @@ export default class NotificationServicesController extends BaseController<
           (notification) => notification.id,
         );
       }
-    } catch (err) {
-      log.warn('Something failed when marking notifications as read', err);
+    } catch (error) {
+      log.warn('Something failed when marking notifications as read', error);
     }
 
     // Update the state (state is also used on counter & badge)
@@ -1268,7 +1278,9 @@ export default class NotificationServicesController extends BaseController<
     notification: INotification,
   ): Promise<void> {
     if (
-      this.state.metamaskNotificationsList.some((n) => n.id === notification.id)
+      this.state.metamaskNotificationsList.some(
+        (existingNotification) => existingNotification.id === notification.id,
+      )
     ) {
       return;
     }
@@ -1278,7 +1290,9 @@ export default class NotificationServicesController extends BaseController<
     if (processedNotification) {
       this.update((state) => {
         const existingNotificationIds = new Set(
-          state.metamaskNotificationsList.map((n) => n.id),
+          state.metamaskNotificationsList.map(
+            (existingNotification) => existingNotification.id,
+          ),
         );
         // Add the new notification only if its ID is not already present in the list
         if (!existingNotificationIds.has(processedNotification.id)) {
@@ -1302,7 +1316,9 @@ export default class NotificationServicesController extends BaseController<
    *
    * @param input perp input
    */
-  public async sendPerpPlaceOrderNotification(input: OrderInput) {
+  public async sendPerpPlaceOrderNotification(
+    input: OrderInput,
+  ): Promise<void> {
     try {
       const { bearerToken } = await this.#getBearerToken();
       await createPerpOrderNotification(bearerToken, input);
diff --git a/packages/notification-services-controller/src/NotificationServicesController/__fixtures__/mockServices.ts b/packages/notification-services-controller/src/NotificationServicesController/__fixtures__/mockServices.ts
index 206b6bb5e97..44ac409c51b 100644
--- a/packages/notification-services-controller/src/NotificationServicesController/__fixtures__/mockServices.ts
+++ b/packages/notification-services-controller/src/NotificationServicesController/__fixtures__/mockServices.ts
@@ -16,7 +16,7 @@ type MockReply = {
 
 export const mockFetchFeatureAnnouncementNotifications = (
   mockReply?: MockReply,
-) => {
+): nock.Scope => {
   const mockResponse = getMockFeatureAnnouncementResponse();
   const reply = mockReply ?? { status: 200, body: mockResponse.response };
   const mockEndpoint = nock(mockResponse.url)
@@ -27,7 +27,9 @@ export const mockFetchFeatureAnnouncementNotifications = (
   return mockEndpoint;
 };
 
-export const mockUpdateOnChainNotifications = (mockReply?: MockReply) => {
+export const mockUpdateOnChainNotifications = (
+  mockReply?: MockReply,
+): nock.Scope => {
   const mockResponse = getMockUpdateOnChainNotifications();
   const reply = mockReply ?? { status: 204 };
 
@@ -38,7 +40,9 @@ export const mockUpdateOnChainNotifications = (mockReply?: MockReply) => {
   return mockEndpoint;
 };
 
-export const mockGetOnChainNotificationsConfig = (mockReply?: MockReply) => {
+export const mockGetOnChainNotificationsConfig = (
+  mockReply?: MockReply,
+): nock.Scope => {
   const mockResponse = getMockOnChainNotificationsConfig();
   const reply = mockReply ?? { status: 200, body: mockResponse.response };
 
@@ -49,7 +53,7 @@ export const mockGetOnChainNotificationsConfig = (mockReply?: MockReply) => {
   return mockEndpoint;
 };
 
-export const mockGetAPINotifications = (mockReply?: MockReply) => {
+export const mockGetAPINotifications = (mockReply?: MockReply): nock.Scope => {
   const mockResponse = getMockListNotificationsResponse();
   const reply = mockReply ?? { status: 200, body: mockResponse.response };
 
@@ -61,7 +65,9 @@ export const mockGetAPINotifications = (mockReply?: MockReply) => {
   return mockEndpoint;
 };
 
-export const mockMarkNotificationsAsRead = (mockReply?: MockReply) => {
+export const mockMarkNotificationsAsRead = (
+  mockReply?: MockReply,
+): nock.Scope => {
   const mockResponse = getMockMarkNotificationsAsReadResponse();
   const reply = mockReply ?? { status: 200 };
 
@@ -72,7 +78,9 @@ export const mockMarkNotificationsAsRead = (mockReply?: MockReply) => {
   return mockEndpoint;
 };
 
-export const mockCreatePerpNotification = (mockReply?: MockReply) => {
+export const mockCreatePerpNotification = (
+  mockReply?: MockReply,
+): nock.Scope => {
   const mockResponse = getMockCreatePerpOrderNotification();
   const reply = mockReply ?? { status: 201 };
   const mockEndpoint = nock(mockResponse.url)