diff --git a/.changes/next-release/bugfix-s3-a752bb97.json b/.changes/next-release/bugfix-s3-a752bb97.json
new file mode 100644
index 0000000000..01f3fb1740
--- /dev/null
+++ b/.changes/next-release/bugfix-s3-a752bb97.json
@@ -0,0 +1,5 @@
+{
+  "type": "bugfix",
+  "category": "s3",
+  "description": "createBucket mutates params argument when endpoint is configured by appending CreateBucketConfigurationon key, this side effect is now fixed"
+}
\ No newline at end of file
diff --git a/lib/services/s3.js b/lib/services/s3.js
index 69553e3c1c..e27aa112b4 100644
--- a/lib/services/s3.js
+++ b/lib/services/s3.js
@@ -1314,10 +1314,14 @@ AWS.util.update(AWS.S3.prototype, {
       params = {};
     }
     var hostname = this.endpoint.hostname;
+    // copy params so that appending keys does not unintentioinallly
+    // mutate params object argument passed in by user
+    var copiedParams = AWS.util.copy(params);
+
     if (hostname !== this.api.globalEndpoint && !params.CreateBucketConfiguration) {
-      params.CreateBucketConfiguration = { LocationConstraint: this.config.region };
+      copiedParams.CreateBucketConfiguration = { LocationConstraint: this.config.region };
     }
-    return this.makeRequest('createBucket', params, callback);
+    return this.makeRequest('createBucket', copiedParams, callback);
   },
 
   /**
diff --git a/test/services/s3.spec.js b/test/services/s3.spec.js
index 9a9fe3a4cc..32d7a7625e 100644
--- a/test/services/s3.spec.js
+++ b/test/services/s3.spec.js
@@ -2391,6 +2391,34 @@ describe('AWS.S3', function() {
         done();
       });
     });
+
+    it('appends CreateBucketConfiguration key to copy of params, not original, when endpoint is configured', function(done) {
+      var loc = null;
+      var params = {
+        Bucket: 'name'
+      };
+
+      s3 = new AWS.S3({
+        region: 'eu-west-1',
+        Bucket: 'name',
+        endpoint: 'https://foo.bar.baz:555/prefix'
+      });
+
+      s3.makeRequest = function(op, copiedParams, cb) {
+        expect(copiedParams).to['be'].a('object');
+        loc = copiedParams.CreateBucketConfiguration.LocationConstraint;
+        if (typeof cb === 'function') {
+          return cb();
+        }
+      };
+
+      helpers.mockHttpResponse(200, {}, '');
+      s3.createBucket(params, function() {
+        expect(params.CreateBucketConfiguration).to.not.exist;
+        expect(loc).to.be.a.string;
+        done();
+      });
+    });
   });
 
   describe('deleteBucket', function() {