diff --git a/gems/aws-sdk-core/CHANGELOG.md b/gems/aws-sdk-core/CHANGELOG.md
index 5051c22d8da..29c45b3f4ce 100644
--- a/gems/aws-sdk-core/CHANGELOG.md
+++ b/gems/aws-sdk-core/CHANGELOG.md
@@ -1,6 +1,8 @@
 Unreleased Changes
 ------------------
 
+* Issue - Make stubs thread safe by creating new responses for each operation call (#2675).
+
 3.129.0 (2022-03-08)
 ------------------
 
diff --git a/gems/aws-sdk-core/lib/aws-sdk-core/client_stubs.rb b/gems/aws-sdk-core/lib/aws-sdk-core/client_stubs.rb
index ea2379be645..c8759098005 100644
--- a/gems/aws-sdk-core/lib/aws-sdk-core/client_stubs.rb
+++ b/gems/aws-sdk-core/lib/aws-sdk-core/client_stubs.rb
@@ -262,13 +262,17 @@ def apply_stubs(operation_name, stubs)
     end
 
     def convert_stub(operation_name, stub)
-      case stub
+      stub = case stub
       when Proc then stub
       when Exception, Class then { error: stub }
       when String then service_error_stub(stub)
       when Hash then http_response_stub(operation_name, stub)
       else { data: stub }
       end
+      if Hash === stub
+        stub[:mutex] = Mutex.new
+      end
+      stub
     end
 
     def service_error_stub(error_code)
diff --git a/gems/aws-sdk-core/lib/aws-sdk-core/plugins/stub_responses.rb b/gems/aws-sdk-core/lib/aws-sdk-core/plugins/stub_responses.rb
index dbfe6a05999..fa8cd7f3e34 100644
--- a/gems/aws-sdk-core/lib/aws-sdk-core/plugins/stub_responses.rb
+++ b/gems/aws-sdk-core/lib/aws-sdk-core/plugins/stub_responses.rb
@@ -51,7 +51,11 @@ def call(context)
           stub = context.client.next_stub(context)
           resp = Seahorse::Client::Response.new(context: context)
           async_mode = context.client.is_a? Seahorse::Client::AsyncBase
-          apply_stub(stub, resp, async_mode)
+          if Hash === stub && stub[:mutex]
+            stub[:mutex].synchronize { apply_stub(stub, resp, async_mode) }
+          else
+            apply_stub(stub, resp, async_mode)
+          end
 
           async_mode ? Seahorse::Client::AsyncResponse.new(
             context: context, stream: context[:input_event_stream_handler].event_emitter.stream, sync_queue: Queue.new) : resp