diff --git a/generator/.DevConfigs/433a9a6d-b8ea-4676-b763-70711e8288e6.json b/generator/.DevConfigs/433a9a6d-b8ea-4676-b763-70711e8288e6.json
new file mode 100644
index 000000000000..5d67e3a8b858
--- /dev/null
+++ b/generator/.DevConfigs/433a9a6d-b8ea-4676-b763-70711e8288e6.json
@@ -0,0 +1,11 @@
+{
+  "services": [
+    {
+      "serviceName": "S3",
+      "type": "patch",
+      "changeLogMessages": [
+        "Added CompleteMultipartUploadResponse to TransferUtilityUploadResponse mapping"
+      ]
+    }
+  ]
+}
diff --git a/sdk/src/Services/S3/Custom/Transfer/Internal/ResponseMapper.cs b/sdk/src/Services/S3/Custom/Transfer/Internal/ResponseMapper.cs
index d130aee20bff..7e8505ecbf69 100644
--- a/sdk/src/Services/S3/Custom/Transfer/Internal/ResponseMapper.cs
+++ b/sdk/src/Services/S3/Custom/Transfer/Internal/ResponseMapper.cs
@@ -99,6 +99,67 @@ internal static TransferUtilityUploadResponse MapPutObjectResponse(PutObjectResp
 
             return response;
         }
+
+        /// <summary>
+        /// Maps a CompleteMultipartUploadResponse to TransferUtilityUploadResponse.
+        /// Uses the field mappings defined in mapping.json "Conversion" -> "CompleteMultipartResponse" -> "UploadResponse".
+        /// </summary>
+        /// <param name="source">The CompleteMultipartUploadResponse to map from</param>
+        /// <returns>A new TransferUtilityUploadResponse with mapped fields</returns>
+        internal static TransferUtilityUploadResponse MapCompleteMultipartUploadResponse(CompleteMultipartUploadResponse source)
+        {
+            if (source == null)
+                return null;
+
+            var response = new TransferUtilityUploadResponse();
+
+            // Map all fields as defined in mapping.json "Conversion" -> "CompleteMultipartResponse" -> "UploadResponse"
+            if (source.IsSetBucketKeyEnabled())
+                response.BucketKeyEnabled = source.BucketKeyEnabled.GetValueOrDefault();
+
+            if (source.IsSetChecksumCRC32())
+                response.ChecksumCRC32 = source.ChecksumCRC32;
+
+            if (source.IsSetChecksumCRC32C())
+                response.ChecksumCRC32C = source.ChecksumCRC32C;
+
+            if (source.IsSetChecksumCRC64NVME())
+                response.ChecksumCRC64NVME = source.ChecksumCRC64NVME;
+
+            if (source.IsSetChecksumSHA1())
+                response.ChecksumSHA1 = source.ChecksumSHA1;
+
+            if (source.IsSetChecksumSHA256())
+                response.ChecksumSHA256 = source.ChecksumSHA256;
+
+            if (source.ChecksumType != null)
+                response.ChecksumType = source.ChecksumType;
+
+            if (source.IsSetETag())
+                response.ETag = source.ETag;
+
+            if (source.Expiration != null)
+                response.Expiration = source.Expiration;
+
+            if (source.IsSetRequestCharged())
+                response.RequestCharged = source.RequestCharged;
+
+            if (source.ServerSideEncryptionMethod != null)
+                response.ServerSideEncryptionMethod = source.ServerSideEncryptionMethod;
+
+            if (source.IsSetServerSideEncryptionKeyManagementServiceKeyId())
+                response.ServerSideEncryptionKeyManagementServiceKeyId = source.ServerSideEncryptionKeyManagementServiceKeyId;
+
+            if (source.IsSetVersionId())
+                response.VersionId = source.VersionId;
+
+            // Copy response metadata
+            response.ResponseMetadata = source.ResponseMetadata;
+            response.ContentLength = source.ContentLength;
+            response.HttpStatusCode = source.HttpStatusCode;
+
+            return response;
+        }
         
     }
 }
diff --git a/sdk/test/Services/S3/UnitTests/Custom/EmbeddedResource/property-aliases.json b/sdk/test/Services/S3/UnitTests/Custom/EmbeddedResource/property-aliases.json
index e9de0a44b4fe..97a29b7695c3 100644
--- a/sdk/test/Services/S3/UnitTests/Custom/EmbeddedResource/property-aliases.json
+++ b/sdk/test/Services/S3/UnitTests/Custom/EmbeddedResource/property-aliases.json
@@ -112,6 +112,10 @@
     },
     "AbortMultipartUploadRequest": {
       "Bucket": "BucketName"
+    },
+    "CompleteMultipartUploadResponse": {
+      "ServerSideEncryption": "ServerSideEncryptionMethod",
+      "SSEKMSKeyId": "ServerSideEncryptionKeyManagementServiceKeyId"
     }
   }
 }
\ No newline at end of file
diff --git a/sdk/test/Services/S3/UnitTests/Custom/ResponseMapperTests.cs b/sdk/test/Services/S3/UnitTests/Custom/ResponseMapperTests.cs
index ca6569d286db..1854c8d79020 100644
--- a/sdk/test/Services/S3/UnitTests/Custom/ResponseMapperTests.cs
+++ b/sdk/test/Services/S3/UnitTests/Custom/ResponseMapperTests.cs
@@ -462,6 +462,56 @@ public void ValidateTransferUtilityUploadResponseDefinitionCompleteness()
                 "TransferUtilityUploadResponse");
         }
 
+        [TestMethod]
+        [TestCategory("S3")]
+        public void MapCompleteMultipartUploadResponse_AllMappedProperties_WorkCorrectly()
+        {
+            ValidateMappingTransferUtilityAndSdkRequests<CompleteMultipartUploadResponse, TransferUtilityUploadResponse>(
+                new[] { "Conversion", "CompleteMultipartResponse", "UploadResponse" },
+                (sourceResponse) =>
+                {
+                    return ResponseMapper.MapCompleteMultipartUploadResponse(sourceResponse);
+                },
+                usesHeadersCollection: false,
+                (sourceResponse) =>
+                {
+                    sourceResponse.HttpStatusCode = HttpStatusCode.OK;
+                    sourceResponse.ContentLength = 2048;
+                },
+                (sourceResponse, targetResponse) =>
+                {
+                    Assert.AreEqual(sourceResponse.HttpStatusCode, targetResponse.HttpStatusCode, "HttpStatusCode should match");
+                    Assert.AreEqual(sourceResponse.ContentLength, targetResponse.ContentLength, "ContentLength should match");
+                });
+        }
+
+        [TestMethod]
+        [TestCategory("S3")]
+        public void MapCompleteMultipartUploadResponse_NullValues_HandledCorrectly()
+        {
+            // Test null handling scenarios
+            var testCases = new[]
+            {
+                // Test null Expiration
+                new CompleteMultipartUploadResponse { Expiration = null },
+                
+                // Test null enum conversions
+                new CompleteMultipartUploadResponse { ChecksumType = null, RequestCharged = null, ServerSideEncryptionMethod = null }
+            };
+
+            foreach (var testCase in testCases)
+            {
+                var mapped = ResponseMapper.MapCompleteMultipartUploadResponse(testCase);
+                Assert.IsNotNull(mapped, "Response should always be mappable");
+
+                // Test null handling
+                if (testCase.Expiration == null)
+                {
+                    Assert.IsNull(mapped.Expiration, "Null Expiration should map to null");
+                }
+            }
+        }
+
         [TestMethod]
         [TestCategory("S3")]
         public void ValidateCompleteMultipartUploadResponseConversionCompleteness()