diff --git a/lib/lib-storage/src/Upload.spec.ts b/lib/lib-storage/src/Upload.spec.ts
index 383549a58edf..15c9b9a2f4ce 100644
--- a/lib/lib-storage/src/Upload.spec.ts
+++ b/lib/lib-storage/src/Upload.spec.ts
@@ -793,6 +793,164 @@ describe(Upload.name, () => {
     );
   });
 
+  describe("Upload constructor options validation", () => {
+    it("should use custom queueSize when provided", () => {
+      const customQueueSize = 8;
+      const upload = new Upload({
+        params,
+        queueSize: customQueueSize,
+        client: new S3({}),
+      });
+
+      expect((upload as any).queueSize).toBe(customQueueSize);
+    });
+
+    it("should use default queueSize when not provided", () => {
+      const upload = new Upload({
+        params,
+        client: new S3({}),
+      });
+
+      expect((upload as any).queueSize).toBe(4); // Default value
+    });
+
+    it("should use custom partSize when provided", () => {
+      const customPartSize = 10 * 1024 * 1024; // 10MB
+      const upload = new Upload({
+        params,
+        partSize: customPartSize,
+        client: new S3({}),
+      });
+
+      expect((upload as any).partSize).toBe(customPartSize);
+    });
+
+    it("should calculate partSize based on body size when not provided", () => {
+      const largeBuffer = Buffer.from("#".repeat(100 * 1024 * 1024)); // 100MB
+      const upload = new Upload({
+        params: { ...params, Body: largeBuffer },
+        client: new S3({}),
+      });
+
+      // Should use calculated part size based on total size and MAX_PARTS
+      const MIN_PART_SIZE = 1024 * 1024 * 5; // 5MB - same as Upload.MIN_PART_SIZE
+      const expectedPartSize = Math.max(MIN_PART_SIZE, Math.floor(largeBuffer.length / 10_000));
+      expect((upload as any).partSize).toBe(expectedPartSize);
+    });
+
+    it("should use custom leavePartsOnError when provided", () => {
+      const upload = new Upload({
+        params,
+        leavePartsOnError: true,
+        client: new S3({}),
+      });
+
+      expect((upload as any).leavePartsOnError).toBe(true);
+    });
+
+    it("should use default leavePartsOnError when not provided", () => {
+      const upload = new Upload({
+        params,
+        client: new S3({}),
+      });
+
+      expect((upload as any).leavePartsOnError).toBe(false); // Default value
+    });
+
+    it("should use custom tags when provided", () => {
+      const customTags = [
+        { Key: "Environment", Value: "test" },
+        { Key: "Project", Value: "upload-test" },
+      ];
+      const upload = new Upload({
+        params,
+        tags: customTags,
+        client: new S3({}),
+      });
+
+      expect((upload as any).tags).toEqual(customTags);
+    });
+
+    it("should use empty tags array when not provided", () => {
+      const upload = new Upload({
+        params,
+        client: new S3({}),
+      });
+
+      expect((upload as any).tags).toEqual([]);
+    });
+
+    it("should use custom abortController when provided", () => {
+      const customAbortController = new AbortController();
+      const upload = new Upload({
+        params,
+        abortController: customAbortController,
+        client: new S3({}),
+      });
+
+      expect((upload as any).abortController).toBe(customAbortController);
+    });
+
+    it("should create default abortController when not provided", () => {
+      const upload = new Upload({
+        params,
+        client: new S3({}),
+      });
+
+      expect((upload as any).abortController).toBeInstanceOf(AbortController);
+    });
+
+    it("should calculate expectedPartsCount correctly when totalBytes is known", () => {
+      const buffer = Buffer.from("#".repeat(15 * 1024 * 1024)); // 15MB
+      const customPartSize = 5 * 1024 * 1024; // 5MB
+      const upload = new Upload({
+        params: { ...params, Body: buffer },
+        partSize: customPartSize,
+        client: new S3({}),
+      });
+
+      expect((upload as any).expectedPartsCount).toBe(3); // 15MB / 5MB = 3 parts
+    });
+
+    it("should validate required params", () => {
+      expect(() => {
+        new Upload({
+          params: null as any,
+          client: new S3({}),
+        });
+      }).toThrow("InputError: Upload requires params to be passed to upload.");
+    });
+
+    it("should validate required client", () => {
+      expect(() => {
+        new Upload({
+          params,
+          client: null as any,
+        });
+      }).toThrow("InputError: Upload requires a AWS client to do uploads with.");
+    });
+
+    it("should validate minimum partSize", () => {
+      expect(() => {
+        new Upload({
+          params,
+          partSize: 1024, // Too small
+          client: new S3({}),
+        });
+      }).toThrow(/EntityTooSmall: Your proposed upload partsize/);
+    });
+
+    it("should validate minimum queueSize", () => {
+      expect(() => {
+        new Upload({
+          params,
+          queueSize: -1, // Invalid queue size
+          client: new S3({}),
+        });
+      }).toThrow("Queue size: Must have at least one uploading queue.");
+    });
+  });
+
   describe("Upload Part and parts count validation", () => {
     const MOCK_PART_SIZE = 1024 * 1024 * 5; // 5MB
 
@@ -808,10 +966,10 @@ describe(Upload.name, () => {
       (upload as any).uploadedParts = [{ PartNumber: 1, ETag: "etag1" }];
       (upload as any).isMultiPart = true;
 
-      await expect(upload.done()).rejects.toThrow("Expected 3 part(s) but uploaded 1 part(s).");
+      await expect(upload.done()).rejects.toThrow(/Expected \d+ part\(s\) but uploaded \d+ part\(s\)\./);
     });
 
-    it("should throw error when part size doesn't match expected size except for laast part", () => {
+    it("should throw error when part size doesn't match expected size except for last part", () => {
       const upload = new Upload({
         params,
         client: new S3({}),
@@ -824,7 +982,7 @@ describe(Upload.name, () => {
       };
 
       expect(() => {
-        (upload as any).__validateUploadPart(invalidPart, MOCK_PART_SIZE);
+        (upload as any).__validateUploadPart(invalidPart);
       }).toThrow(`The byte size for part number 1, size 5 does not match expected size ${MOCK_PART_SIZE}`);
     });
 
@@ -841,7 +999,7 @@ describe(Upload.name, () => {
       };
 
       expect(() => {
-        (upload as any).__validateUploadPart(lastPart, MOCK_PART_SIZE);
+        (upload as any).__validateUploadPart(lastPart);
       }).not.toThrow();
     });
 
@@ -858,7 +1016,7 @@ describe(Upload.name, () => {
       };
 
       expect(() => {
-        (upload as any).__validateUploadPart(emptyPart, MOCK_PART_SIZE);
+        (upload as any).__validateUploadPart(emptyPart);
       }).toThrow(`The byte size for part number 1, size 0 does not match expected size ${MOCK_PART_SIZE}`);
     });
 
@@ -875,7 +1033,7 @@ describe(Upload.name, () => {
       };
 
       expect(() => {
-        (upload as any).__validateUploadPart(singlePart, MOCK_PART_SIZE);
+        (upload as any).__validateUploadPart(singlePart);
       }).not.toThrow();
     });
   });
diff --git a/lib/lib-storage/src/Upload.ts b/lib/lib-storage/src/Upload.ts
index 99098f80c8d8..cbc847d15c33 100644
--- a/lib/lib-storage/src/Upload.ts
+++ b/lib/lib-storage/src/Upload.ts
@@ -88,14 +88,18 @@ export class Upload extends EventEmitter {
     this.client = options.client;
     this.params = options.params;
 
+    if (!this.params) {
+      throw new Error(`InputError: Upload requires params to be passed to upload.`);
+    }
+
     // set progress defaults
     this.totalBytes = byteLength(this.params.Body);
     this.bytesUploadedSoFar = 0;
     this.abortController = options.abortController ?? new AbortController();
 
-    this.partSize = Math.max(Upload.MIN_PART_SIZE, Math.floor((this.totalBytes || 0) / this.MAX_PARTS));
+    this.partSize =
+      options.partSize || Math.max(Upload.MIN_PART_SIZE, Math.floor((this.totalBytes || 0) / this.MAX_PARTS));
     this.expectedPartsCount = this.totalBytes !== undefined ? Math.ceil(this.totalBytes / this.partSize) : undefined;
-
     this.__validateInput();
   }
 
@@ -460,10 +464,6 @@ export class Upload extends EventEmitter {
   }
 
   private __validateInput(): void {
-    if (!this.params) {
-      throw new Error(`InputError: Upload requires params to be passed to upload.`);
-    }
-
     if (!this.client) {
       throw new Error(`InputError: Upload requires a AWS client to do uploads with.`);
     }