diff --git a/scrapy/extensions/feedexport.py b/scrapy/extensions/feedexport.py
index 70c302fba..067887d94 100644
--- a/scrapy/extensions/feedexport.py
+++ b/scrapy/extensions/feedexport.py
@@ -93,12 +93,28 @@ class FileFeedStorage(object):
 
 class S3FeedStorage(BlockingFeedStorage):
 
-    def __init__(self, uri):
+    def __init__(self, uri, access_key=None, secret_key=None):
+        # BEGIN Backwards compatibility for initialising without keys (and
+        # without using from_crawler)
         from scrapy.conf import settings
+        no_defaults = access_key is None and secret_key is None
+        if no_defaults and ('AWS_ACCESS_KEY_ID' in settings or
+                            'AWS_SECRET_ACCESS_KEY' in settings):
+            import warnings
+            from scrapy.exceptions import ScrapyDeprecationWarning
+            warnings.warn(
+                "Initialising `scrapy.extensions.feedexport.S3FeedStorage` "
+                "without AWS keys is deprecated. Please supply credentials or "
+                "use the `from_crawler()` constructor.",
+                category=ScrapyDeprecationWarning,
+                stacklevel=2
+            )
+            access_key = settings['AWS_ACCESS_KEY_ID']
+            secret_key = settings['AWS_SECRET_ACCESS_KEY']
         u = urlparse(uri)
         self.bucketname = u.hostname
-        self.access_key = u.username or settings['AWS_ACCESS_KEY_ID']
-        self.secret_key = u.password or settings['AWS_SECRET_ACCESS_KEY']
+        self.access_key = u.username or access_key
+        self.secret_key = u.password or secret_key
         self.is_botocore = is_botocore()
         self.keyname = u.path[1:]  # remove first "/"
         if self.is_botocore:
@@ -111,6 +127,11 @@ class S3FeedStorage(BlockingFeedStorage):
             import boto
             self.connect_s3 = boto.connect_s3
 
+    @classmethod
+    def from_crawler(cls, crawler, uri):
+        return cls(uri, crawler.settings['AWS_ACCESS_KEY_ID'],
+                   crawler.settings['AWS_SECRET_ACCESS_KEY'])
+
     def _store_in_thread(self, file):
         file.seek(0)
         if self.is_botocore:
diff --git a/tests/test_feedexport.py b/tests/test_feedexport.py
index 08f7e4d8d..eeb1bc2a4 100644
--- a/tests/test_feedexport.py
+++ b/tests/test_feedexport.py
@@ -6,12 +6,14 @@ from io import BytesIO
 import tempfile
 import shutil
 from six.moves.urllib.parse import urlparse
+import warnings
 
 from zope.interface.verify import verifyObject
 from twisted.trial import unittest
 from twisted.internet import defer
 from scrapy.crawler import CrawlerRunner
 from scrapy.settings import Settings
+from tests import mock
 from tests.mockserver import MockServer
 from w3lib.url import path_to_file_uri
 
@@ -131,13 +133,47 @@ class BlockingFeedStorageTest(unittest.TestCase):
 
 class S3FeedStorageTest(unittest.TestCase):
 
+    @mock.patch('scrapy.conf.settings', new={'AWS_ACCESS_KEY_ID': 'conf_key',
+                'AWS_SECRET_ACCESS_KEY': 'conf_secret'}, create=True)
+    def test_parse_credentials(self):
+        try:
+            import boto
+        except ImportError:
+            raise unittest.SkipTest("S3FeedStorage requires boto")
+        aws_credentials = {'AWS_ACCESS_KEY_ID': 'settings_key',
+                           'AWS_SECRET_ACCESS_KEY': 'settings_secret'}
+        crawler = get_crawler(settings_dict=aws_credentials)
+        # Instantiate with crawler
+        storage = S3FeedStorage.from_crawler(crawler,
+                                             's3://mybucket/export.csv')
+        self.assertEqual(storage.access_key, 'settings_key')
+        self.assertEqual(storage.secret_key, 'settings_secret')
+        # Instantiate directly
+        storage = S3FeedStorage('s3://mybucket/export.csv',
+                                aws_credentials['AWS_ACCESS_KEY_ID'],
+                                aws_credentials['AWS_SECRET_ACCESS_KEY'])
+        self.assertEqual(storage.access_key, 'settings_key')
+        self.assertEqual(storage.secret_key, 'settings_secret')
+        # URI priority > settings priority
+        storage = S3FeedStorage('s3://uri_key:uri_secret@mybucket/export.csv',
+                                aws_credentials['AWS_ACCESS_KEY_ID'],
+                                aws_credentials['AWS_SECRET_ACCESS_KEY'])
+        self.assertEqual(storage.access_key, 'uri_key')
+        self.assertEqual(storage.secret_key, 'uri_secret')
+        # Backwards compatibility for initialising without settings
+        with warnings.catch_warnings(record=True) as w:
+            storage = S3FeedStorage('s3://mybucket/export.csv')
+            self.assertEqual(storage.access_key, 'conf_key')
+            self.assertEqual(storage.secret_key, 'conf_secret')
+            self.assertTrue('without AWS keys' in str(w[-1].message))
+
     @defer.inlineCallbacks
     def test_store(self):
         assert_aws_environ()
         uri = os.environ.get('S3_TEST_FILE_URI')
         if not uri:
             raise unittest.SkipTest("No S3 URI available for testing")
-        storage = S3FeedStorage(uri)
+        storage = S3FeedStorage(uri, Settings())
         verifyObject(IFeedStorage, storage)
         file = storage.open(scrapy.Spider("default"))
         expected_content = b"content: \xe2\x98\x83"