diff --git a/Lib/test/test_urllib2net.py b/Lib/test/test_urllib2net.py
--- a/Lib/test/test_urllib2net.py
+++ b/Lib/test/test_urllib2net.py
@@ -176,19 +176,36 @@ class OtherNetworkTests(unittest.TestCas
         url = "http://www.example.com"
         with support.transient_internet(url):
             opener = urllib.request.build_opener()
             request = urllib.request.Request(url)
             self.assertFalse(request.header_items())
             opener.open(request)
             self.assertTrue(request.header_items())
             self.assertTrue(request.has_header('User-agent'))
-            request.add_header('User-Agent','Test-Agent')
+            request.add_header('User-Agent', 'Test-Agent')
             opener.open(request)
-            self.assertEqual(request.get_header('User-agent'),'Test-Agent')
+            self.assertEqual(request.get_header('User-Agent'), 'Test-Agent')
+
+    def test_headers_case_sensitivity(self):
+        url = "http://www.example.com"
+        with support.transient_internet(url):
+            opener = urllib.request.build_opener()
+            request = urllib.request.Request(url)
+            headers = [("Content-Type", "text/plain"), ]
+            opener.addheaders = headers
+            opener.open(request)
+            self.assertTrue(request.has_header('Content-type'))
+            self.assertTrue(request.has_header('Content-Type'))
+            self.assertTrue(request.has_header('content-type'))
+            self.assertTrue(request.has_header('CoNtEnT-tYpE'))
+            self.assertEqual(request.get_header('Content-type'), 'text/plain')
+            self.assertEqual(request.get_header('Content-Type'), 'text/plain')
+            self.assertEqual(request.get_header('content-type'), 'text/plain')
+            self.assertEqual(request.get_header('CoNtEnT-tYpE'), 'text/plain')
 
     def test_sites_no_connection_close(self):
         # Some sites do not send Connection: close header.
         # Verify that those work properly. (#issue12576)
 
         URL = 'http://www.imdb.com' # mangles Connection:close
 
         with support.transient_internet(URL):
diff --git a/Lib/urllib/request.py b/Lib/urllib/request.py
--- a/Lib/urllib/request.py
+++ b/Lib/urllib/request.py
@@ -346,23 +346,30 @@ class Request:
         # useful for something like authentication
         self.headers[key.capitalize()] = val
 
     def add_unredirected_header(self, key, val):
         # will not be added to a redirected request
         self.unredirected_hdrs[key.capitalize()] = val
 
     def has_header(self, header_name):
-        return (header_name in self.headers or
-                header_name in self.unredirected_hdrs)
+        lower_hdr = header_name.lower()
+        return (lower_hdr in [key.lower() for key in self.headers] or
+                lower_hdr in [key.lower() for key in self.unredirected_hdrs])
 
     def get_header(self, header_name, default=None):
-        return self.headers.get(
-            header_name,
-            self.unredirected_hdrs.get(header_name, default))
+        lower_hdr = header_name.lower()
+        hdr_value = [value for key, value in self.headers.items()
+                     if key.lower() == lower_hdr] or None
+        if not hdr_value:
+            hdr_value = [value for key, value in self.unredirected_hdrs.items()
+                         if key.lower() == lower_hdr] or None
+        if hdr_value:
+            return hdr_value[0]
+        return hdr_value
 
     def remove_header(self, header_name):
         self.headers.pop(header_name, None)
         self.unredirected_hdrs.pop(header_name, None)
 
     def header_items(self):
         hdrs = self.unredirected_hdrs.copy()
         hdrs.update(self.headers)