diff --git a/awscli/customizations/s3/syncstrategy/ignoreexisting.py b/awscli/customizations/s3/syncstrategy/ignoreexisting.py
new file mode 100644
index 000000000000..807778836737
--- /dev/null
+++ b/awscli/customizations/s3/syncstrategy/ignoreexisting.py
@@ -0,0 +1,34 @@
+# Copyright 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"). You
+# may not use this file except in compliance with the License. A copy of
+# the License is located at
+#
+# http://aws.amazon.com/apache2.0/
+#
+# or in the "license" file accompanying this file. This file is
+# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
+# ANY KIND, either express or implied. See the License for the specific
+# language governing permissions and limitations under the License.
+import logging
+
+from awscli.customizations.s3.syncstrategy.base import BaseSync
+
+
+LOG = logging.getLogger(__name__)
+
+
+IGNORE_EXISTING = {
+    'name': 'ignore_existing',
+    'action': 'store_true',
+    'help_text': ('If the file exists, do not sync.')
+}
+
+
+class IgnoreExistingSync(BaseSync):
+
+    ARGUMENT = IGNORE_EXISTING
+
+    def determine_should_sync(self, src_file, dest_file):
+        LOG.debug("ignoring existing file %s", src_file)
+        return False
diff --git a/awscli/customizations/s3/syncstrategy/register.py b/awscli/customizations/s3/syncstrategy/register.py
index b75674dcb99b..f31d39a56732 100644
--- a/awscli/customizations/s3/syncstrategy/register.py
+++ b/awscli/customizations/s3/syncstrategy/register.py
@@ -14,6 +14,8 @@
 from awscli.customizations.s3.syncstrategy.exacttimestamps import \
     ExactTimestampsSync
 from awscli.customizations.s3.syncstrategy.delete import DeleteSync
+from awscli.customizations.s3.syncstrategy.ignoreexisting import \
+    IgnoreExistingSync
 
 
 def register_sync_strategy(session, strategy_cls,
@@ -46,4 +48,7 @@ def register_sync_strategies(command_table, session, **kwargs):
     # Register the delete sync strategy.
     register_sync_strategy(session, DeleteSync, 'file_not_at_src')
 
+    # Register the sync once strategy.
+    register_sync_strategy(session, IgnoreExistingSync)
+
     # Register additional sync strategies here...
diff --git a/tests/unit/customizations/s3/syncstrategy/test_ignoreexisting.py b/tests/unit/customizations/s3/syncstrategy/test_ignoreexisting.py
new file mode 100644
index 000000000000..b8a4c2a2d9f7
--- /dev/null
+++ b/tests/unit/customizations/s3/syncstrategy/test_ignoreexisting.py
@@ -0,0 +1,70 @@
+# Copyright 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"). You
+# may not use this file except in compliance with the License. A copy of
+# the License is located at
+#
+# http://aws.amazon.com/apache2.0/
+#
+# or in the "license" file accompanying this file. This file is
+# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
+# ANY KIND, either express or implied. See the License for the specific
+# language governing permissions and limitations under the License.
+import datetime
+
+from awscli.customizations.s3.filegenerator import FileStat
+from awscli.customizations.s3.syncstrategy.ignoreexisting import \
+    IgnoreExistingSync
+
+from awscli.testutils import unittest
+
+
+class TestIgnoreExistingSync(unittest.TestCase):
+    def setUp(self):
+        self.sync_strategy = IgnoreExistingSync()
+
+    def test_same_name_download(self):
+        """
+        Confirm that files with the same name are not synced.
+        """
+        time_src = datetime.datetime.now()
+        time_dst = time_src + datetime.timedelta(days=1)
+
+        src_file = FileStat(src='', dest='',
+                            compare_key='test.py', size=10,
+                            last_update=time_src, src_type='local',
+                            dest_type='s3', operation_name='upload')
+
+        dst_file = FileStat(src='', dest='',
+                            compare_key='test.py', size=11,
+                            last_update=time_dst, src_type='s3',
+                            dest_type='local', operation_name='')
+
+        should_sync = self.sync_strategy.determine_should_sync(
+            src_file, dst_file)
+        self.assertFalse(should_sync)
+
+    def test_same_name_upload(self):
+        """
+        Confirm that files with the same name are not synced.
+        """
+        time_src = datetime.datetime.now()
+        time_dst = time_src + datetime.timedelta(days=1)
+
+        src_file = FileStat(src='', dest='',
+                            compare_key='test.py', size=10,
+                            last_update=time_src, src_type='s3',
+                            dest_type='local', operation_name='download')
+
+        dst_file = FileStat(src='', dest='',
+                            compare_key='test.py', size=11,
+                            last_update=time_dst, src_type='local',
+                            dest_type='s3', operation_name='')
+
+        should_sync = self.sync_strategy.determine_should_sync(
+            src_file, dst_file)
+        self.assertFalse(should_sync)
+
+
+if __name__ == "__main__":
+    unittest.main()