diff --git a/moto/s3/models.py b/moto/s3/models.py
index 67c48beb..a5fddda9 100644
--- a/moto/s3/models.py
+++ b/moto/s3/models.py
@@ -63,12 +63,8 @@ class FakeMultipart(object):
     def complete(self):
         total = bytearray()
 
-        for part_id, index in enumerate(sorted(self.parts.keys()), start=1):
-            # Make sure part ids are continuous
-            if part_id != index:
-                return
-
-            total.extend(self.parts[part_id].value)
+        for part in self.list_parts():
+            total.extend(part.value)
 
         if len(total) < 5242880:
             return
@@ -83,6 +79,17 @@ class FakeMultipart(object):
         self.parts[part_id] = key
         return key
 
+    def list_parts(self):
+        parts = []
+
+        for part_id, index in enumerate(sorted(self.parts.keys()), start=1):
+            # Make sure part ids are continuous
+            if part_id != index:
+                return
+            parts.append(self.parts[part_id])
+
+        return parts
+
 
 class FakeBucket(object):
     def __init__(self, name):
@@ -156,6 +163,10 @@ class S3Backend(BaseBackend):
 
         return self.set_key(bucket_name, multipart.key_name, value)
 
+    def list_multipart(self, bucket_name, multipart_id):
+        bucket = self.buckets[bucket_name]
+        return bucket.multiparts[multipart_id].list_parts()
+
     def set_part(self, bucket_name, multipart_id, part_id, value):
         bucket = self.buckets[bucket_name]
         multipart = bucket.multiparts[multipart_id]
diff --git a/moto/s3/responses.py b/moto/s3/responses.py
index fe37c6f8..a0a6a698 100644
--- a/moto/s3/responses.py
+++ b/moto/s3/responses.py
@@ -122,6 +122,17 @@ def _key_response(request, full_url, headers):
         body = request.data
 
     if method == 'GET':
+        if 'uploadId' in query:
+            upload_id = query['uploadId'][0]
+            parts = s3_backend.list_multipart(bucket_name, upload_id)
+            template = Template(S3_MULTIPART_LIST_RESPONSE)
+            return 200, headers, template.render(
+                bucket_name=bucket_name,
+                key_name=key_name,
+                upload_id=upload_id,
+                count=len(parts),
+                parts=parts
+                )
         key = s3_backend.get_key(bucket_name, key_name)
         if key:
             headers.update(key.metadata)
@@ -316,6 +327,35 @@ S3_MULTIPART_UPLOAD_RESPONSE = """<?xml version="1.0" encoding="UTF-8"?>
   <ETag>{{ part.etag }}</ETag>
 </CopyPartResult>"""
 
+S3_MULTIPART_LIST_RESPONSE = """<?xml version="1.0" encoding="UTF-8"?>
+<ListPartsResult xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
+  <Bucket>{{ bucket_name }}</Bucket>
+  <Key>{{ key_name }}</Key>
+  <UploadId>{{ upload_id }}</UploadId>
+  <StorageClass>STANDARD</StorageClass>
+  <Initiator>
+    <ID>75aa57f09aa0c8caeab4f8c24e99d10f8e7faeebf76c078efc7c6caea54ba06a</ID>
+    <DisplayName>webfile</DisplayName>
+  </Initiator>
+  <Owner>
+    <ID>75aa57f09aa0c8caeab4f8c24e99d10f8e7faeebf76c078efc7c6caea54ba06a</ID>
+    <DisplayName>webfile</DisplayName>
+  </Owner>
+  <StorageClass>STANDARD</StorageClass>
+  <PartNumberMarker>1</PartNumberMarker>
+  <NextPartNumberMarker>{{ count }} </NextPartNumberMarker>
+  <MaxParts>{{ count }}</MaxParts>
+  <IsTruncated>false</IsTruncated>
+  {% for part in parts %}
+  <Part>
+    <PartNumber>{{ part.name }}</PartNumber>
+    <LastModified>{{ part.last_modified_ISO8601 }}</LastModified>
+    <ETag>{{ part.etag }}</ETag>
+    <Size>{{ part.size }}</Size>
+  </Part>
+  {% endfor %}
+</ListPartsResult>"""
+
 S3_MULTIPART_COMPLETE_RESPONSE = """<?xml version="1.0" encoding="UTF-8"?>
 <CompleteMultipartUploadResult xmlns="http://s3.amazonaws.com/doc/2006-03-01/">
   <Location>http://{{ bucket_name }}.s3.amazonaws.com/{{ key_name }}</Location>