diff --git a/.changes/next-release/bugfix-SSEC-65150.json b/.changes/next-release/bugfix-SSEC-65150.json
new file mode 100644
index 000000000000..de684e1ec9e7
--- /dev/null
+++ b/.changes/next-release/bugfix-SSEC-65150.json
@@ -0,0 +1,5 @@
+{
+  "type": "bugfix",
+  "category": "``SSE-C``",
+  "description": "Pass SSECustomer* arguments to CompleteMultipartUpload for upload operations"
+}
diff --git a/awscli/botocore/handlers.py b/awscli/botocore/handlers.py
index 2ff0625fda2b..6b846b26fa9c 100644
--- a/awscli/botocore/handlers.py
+++ b/awscli/botocore/handlers.py
@@ -1125,6 +1125,7 @@ def customize_endpoint_resolver_builtins(
     ('before-parameter-build.s3.UploadPart', sse_md5),
     ('before-parameter-build.s3.UploadPartCopy', sse_md5),
     ('before-parameter-build.s3.UploadPartCopy', copy_source_sse_md5),
+    ('before-parameter-build.s3.CompleteMultipartUpload', sse_md5),
     ('before-parameter-build.ec2.RunInstances', base64_encode_user_data),
     ('before-parameter-build.auto-scaling.CreateLaunchConfiguration',
      base64_encode_user_data),
diff --git a/awscli/s3transfer/copies.py b/awscli/s3transfer/copies.py
index a1dfdc8ba390..3cd8ef04fa01 100644
--- a/awscli/s3transfer/copies.py
+++ b/awscli/s3transfer/copies.py
@@ -69,7 +69,13 @@ class CopySubmissionTask(SubmissionTask):
         'TaggingDirective',
     ]
 
-    COMPLETE_MULTIPART_ARGS = ['RequestPayer', 'ExpectedBucketOwner']
+    COMPLETE_MULTIPART_ARGS = [
+        'SSECustomerKey',
+        'SSECustomerAlgorithm',
+        'SSECustomerKeyMD5',
+        'RequestPayer',
+        'ExpectedBucketOwner',
+    ]
 
     def _submit(
         self, client, config, osutil, request_executor, transfer_future
diff --git a/awscli/s3transfer/upload.py b/awscli/s3transfer/upload.py
index 18368e0e363a..b864b97d0ac3 100644
--- a/awscli/s3transfer/upload.py
+++ b/awscli/s3transfer/upload.py
@@ -521,7 +521,13 @@ class UploadSubmissionTask(SubmissionTask):
         'ExpectedBucketOwner',
     ]
 
-    COMPLETE_MULTIPART_ARGS = ['RequestPayer', 'ExpectedBucketOwner']
+    COMPLETE_MULTIPART_ARGS = [
+        'SSECustomerKey',
+        'SSECustomerAlgorithm',
+        'SSECustomerKeyMD5',
+        'RequestPayer',
+        'ExpectedBucketOwner',
+    ]
 
     def _get_upload_input_manager_cls(self, transfer_future):
         """Retrieves a class for managing input for an upload based on file type
diff --git a/tests/functional/s3transfer/test_copy.py b/tests/functional/s3transfer/test_copy.py
index 86f05cbfd229..9fde743c9628 100644
--- a/tests/functional/s3transfer/test_copy.py
+++ b/tests/functional/s3transfer/test_copy.py
@@ -481,7 +481,9 @@ def test_copy_passes_args_to_create_multipart_and_upload_part(self):
         self.add_head_object_response(expected_params=head_params)
 
         self._add_params_to_expected_params(
-            add_copy_kwargs, ['create_mpu', 'copy'], self.extra_args
+            add_copy_kwargs,
+            ['create_mpu', 'copy', 'complete_mpu'],
+            self.extra_args,
         )
         self.add_successful_copy_responses(**add_copy_kwargs)
 
diff --git a/tests/functional/s3transfer/test_upload.py b/tests/functional/s3transfer/test_upload.py
index 9f2a4d63ce18..cf61ecb3eb66 100644
--- a/tests/functional/s3transfer/test_upload.py
+++ b/tests/functional/s3transfer/test_upload.py
@@ -599,3 +599,28 @@ def test_multipart_upload_passes_checksums(self):
         )
         future.result()
         self.assert_expected_client_calls_were_correct()
+
+    def test_multipart_upload_with_ssec_args(self):
+        params = {
+            'RequestPayer': 'requester',
+            'SSECustomerKey': 'key',
+            'SSECustomerAlgorithm': 'AES256',
+            'SSECustomerKeyMD5': 'key-hash',
+        }
+        self.extra_args.update(params)
+
+        self.add_create_multipart_response_with_default_expected_params(
+            extra_expected_params=params
+        )
+
+        self.add_upload_part_responses_with_default_expected_params(
+            extra_expected_params=params
+        )
+        self.add_complete_multipart_response_with_default_expected_params(
+            extra_expected_params=params
+        )
+        future = self.manager.upload(
+            self.filename, self.bucket, self.key, self.extra_args
+        )
+        future.result()
+        self.assert_expected_client_calls_were_correct()