diff --git a/packages/manager/src/features/IAM/Delegations/UpdateDelegationForm.tsx b/packages/manager/src/features/IAM/Delegations/UpdateDelegationForm.tsx
index 80d2310f186..a5d6b9c347b 100644
--- a/packages/manager/src/features/IAM/Delegations/UpdateDelegationForm.tsx
+++ b/packages/manager/src/features/IAM/Delegations/UpdateDelegationForm.tsx
@@ -1,5 +1,6 @@
 import {
   useAccountUsersInfiniteQuery,
+  useAllAccountUsersQuery,
   useUpdateChildAccountDelegatesQuery,
 } from '@linode/queries';
 import { ActionsPanel, Autocomplete, Notice, Typography } from '@linode/ui';
@@ -41,6 +42,7 @@ export const UpdateDelegationForm = ({
 }: DelegationsFormProps) => {
   const theme = useTheme();
   const [inputValue, setInputValue] = React.useState<string>('');
+  const [allUserSelected, setAllUserSelected] = React.useState<boolean>(false);
   const debouncedInputValue = useDebouncedValue(inputValue);
 
   const { data: permissions } = usePermissions('account', [
@@ -55,13 +57,35 @@ export const UpdateDelegationForm = ({
   const { data, error, fetchNextPage, hasNextPage, isFetching } =
     useAccountUsersInfiniteQuery(apiFilter);
 
+  const {
+    data: allUsers,
+    isFetching: isFetchingAllUsers,
+    refetch: refetchAllUsers,
+  } = useAllAccountUsersQuery(allUserSelected, {
+    user_type: 'parent',
+  });
+
   const users =
-    data?.pages.flatMap((page) => {
-      return page.data.map((user) => ({
-        label: user.username,
-        value: user.username,
-      }));
-    }) ?? [];
+    allUserSelected && allUsers
+      ? allUsers.map((user) => ({
+          label: user.username,
+          value: user.username,
+        }))
+      : (data?.pages.flatMap((page) => {
+          return page.data.map((user) => ({
+            label: user.username,
+            value: user.username,
+          }));
+        }) ?? []);
+
+  const isSearching =
+    inputValue.length > 0 && debouncedInputValue !== inputValue;
+
+  const isLoadingOptions = isFetching || isFetchingAllUsers;
+
+  const showNoOptionsText = !isLoadingOptions && !isSearching;
+
+  const isSelectAllFetching = allUserSelected && isFetchingAllUsers;
 
   const { mutateAsync: updateDelegates } =
     useUpdateChildAccountDelegatesQuery();
@@ -78,6 +102,7 @@ export const UpdateDelegationForm = ({
     handleSubmit,
     reset,
     setError,
+    setValue,
   } = form;
 
   const onSubmit = async (values: UpdateDelegationsFormValues) => {
@@ -99,9 +124,21 @@ export const UpdateDelegationForm = ({
     }
   };
 
+  const onSelectAllClick = async () => {
+    setAllUserSelected(true);
+    const { data } = await refetchAllUsers();
+    if (data) {
+      setValue(
+        'users',
+        data.map((user) => ({ label: user.username, value: user.username }))
+      );
+    }
+  };
+
   const handleClose = () => {
     reset();
     onClose();
+    setAllUserSelected(false);
   };
 
   return (
@@ -135,20 +172,27 @@ export const UpdateDelegationForm = ({
             render={({ field, fieldState }) => (
               <Autocomplete
                 data-testid="delegates-autocomplete"
+                disabled={isFetchingAllUsers}
                 errorText={fieldState.error?.message ?? error?.[0].reason}
                 isOptionEqualToValue={(option, value) =>
                   option.value === value.value
                 }
-                label={'Delegate Users'}
-                loading={isFetching}
+                label="Delegate Users"
+                loading={isFetching || isFetchingAllUsers}
                 multiple
                 noMarginTop
+                noOptionsText={showNoOptionsText ? 'No users found' : ' '}
                 onChange={(_, newValue) => {
                   field.onChange(newValue || []);
                 }}
                 onInputChange={(_, value) => {
                   setInputValue(value);
                 }}
+                onSelectAllClick={(isSelectAllActive) => {
+                  if (isSelectAllActive && !allUserSelected) {
+                    onSelectAllClick();
+                  }
+                }}
                 options={users}
                 placeholder={getPlaceholder(
                   'delegates',
@@ -171,6 +215,12 @@ export const UpdateDelegationForm = ({
                 }}
                 textFieldProps={{
                   hideLabel: true,
+                  helperText: isSelectAllFetching
+                    ? 'Fetching all users...'
+                    : undefined,
+                  InputProps: isSelectAllFetching
+                    ? { startAdornment: null }
+                    : undefined,
                 }}
                 value={field.value}
               />
diff --git a/packages/ui/src/components/Autocomplete/Autocomplete.tsx b/packages/ui/src/components/Autocomplete/Autocomplete.tsx
index 2dd35db0ca3..060b7888848 100644
--- a/packages/ui/src/components/Autocomplete/Autocomplete.tsx
+++ b/packages/ui/src/components/Autocomplete/Autocomplete.tsx
@@ -48,6 +48,10 @@ export interface EnhancedAutocompleteProps<
   noMarginTop?: boolean;
   /** Element to show when the Autocomplete search yields no results. */
   noOptionsText?: JSX.Element | string;
+  /** Handler called when the Select All option is clicked. */
+  onSelectAllClick?: (
+    event: React.MouseEvent<HTMLLIElement, MouseEvent>,
+  ) => void;
   placeholder?: string;
   renderInput?: (_params: AutocompleteRenderInputParams) => React.ReactNode;
   /** Label for the "select all" option. */
@@ -96,6 +100,7 @@ export const Autocomplete = <
     keepSearchEnabledOnMobile = false,
     onBlur,
     onChange,
+    onSelectAllClick,
     options,
     placeholder,
     renderInput,
@@ -191,6 +196,18 @@ export const Autocomplete = <
         const isSelectAllOption = option === selectAllOption;
         const ListItem = isSelectAllOption ? StyledListItem : 'li';
 
+        // If this is the Select All option, add a click handler
+        const handleClick = (
+          event: React.MouseEvent<HTMLLIElement, MouseEvent>,
+        ) => {
+          if (isSelectAllOption && onSelectAllClick) {
+            onSelectAllClick(event);
+          }
+          if (props.onClick) {
+            props.onClick(event);
+          }
+        };
+
         return renderOption ? (
           renderOption(props, option, state, ownerState)
         ) : (
@@ -198,9 +215,10 @@ export const Autocomplete = <
             {...props}
             data-pendo-id={
               rest.getOptionLabel ? rest.getOptionLabel(option) : option.label
-            } // Adding data-pendo-id for better tracking in Pendo analytics, using the option label as the identifier for the option element.
+            }
             data-qa-option
             key={props.key}
+            onClick={isSelectAllOption ? handleClick : props.onClick}
           >
             <>
               <Box