diff --git a/googleapiclient/errors.py b/googleapiclient/errors.py
index 6656bd1..3d44de7 100644
--- a/googleapiclient/errors.py
+++ b/googleapiclient/errors.py
@@ -37,6 +37,8 @@
   @util.positional(3)
   def __init__(self, resp, content, uri=None):
     self.resp = resp
+    if not isinstance(content, bytes):
+        raise TypeError("HTTP content should be bytes")
     self.content = content
     self.uri = uri
 
@@ -44,7 +46,7 @@
     """Calculate the reason for the error from the response content."""
     reason = self.resp.reason
     try:
-      data = json.loads(self.content)
+      data = json.loads(self.content.decode('utf-8'))
       reason = data['error']['message']
     except (ValueError, KeyError):
       pass
diff --git a/googleapiclient/http.py b/googleapiclient/http.py
index d09483c..0dab8b8 100644
--- a/googleapiclient/http.py
+++ b/googleapiclient/http.py
@@ -1257,6 +1257,10 @@
 
     # Prepend with a content-type header so FeedParser can handle it.
     header = 'content-type: %s\r\n\r\n' % resp['content-type']
+    # PY3's FeedParser only accepts unicode. So we should decode content
+    # here, and encode each payload again.
+    if six.PY3:
+      content = content.decode('utf-8')
     for_parser = header + content
 
     parser = FeedParser()
@@ -1270,6 +1274,9 @@
     for part in mime_response.get_payload():
       request_id = self._header_to_id(part['Content-ID'])
       response, content = self._deserialize_response(part.get_payload())
+      # We encode content here to emulate normal http response.
+      if isinstance(content, six.text_type):
+        content = content.encode('utf-8')
       self._responses[request_id] = (response, content)
 
   @util.positional(1)
@@ -1536,6 +1543,8 @@
         content = body
     elif content == 'echo_request_uri':
       content = uri
+    if isinstance(content, six.text_type):
+      content = content.encode('utf-8')
     return httplib2.Response(resp), content
 
 
diff --git a/tests/test_discovery.py b/tests/test_discovery.py
index e2677b0..1f2b38c 100644
--- a/tests/test_discovery.py
+++ b/tests/test_discovery.py
@@ -1048,7 +1048,7 @@
           'Content-Range': 'bytes */14',
           'content-length': '0'
           }
-      self.assertEqual(expected, json.loads(e.content),
+      self.assertEqual(expected, json.loads(e.content.decode('utf-8')),
         'Should send an empty body when requesting the current upload status.')
 
   def test_pickle(self):
@@ -1186,7 +1186,7 @@
       ({'status': '200'}, 'standing in for media'),
       ])
     response = request.execute(http=http)
-    self.assertEqual('standing in for media', response)
+    self.assertEqual(b'standing in for media', response)
 
 
 if __name__ == '__main__':
diff --git a/tests/test_errors.py b/tests/test_errors.py
index 9af8490..8a58030 100644
--- a/tests/test_errors.py
+++ b/tests/test_errors.py
@@ -28,7 +28,7 @@
 from googleapiclient.errors import HttpError
 
 
-JSON_ERROR_CONTENT = """
+JSON_ERROR_CONTENT = b"""
 {
  "error": {
   "errors": [
@@ -65,7 +65,7 @@
 
   def test_bad_json_body(self):
     """Test handling of bodies with invalid json."""
-    resp, content = fake_response('{',
+    resp, content = fake_response(b'{',
         { 'status':'400', 'content-type': 'application/json'},
         reason='Failed')
     error = HttpError(resp, content)
@@ -73,7 +73,7 @@
 
   def test_with_uri(self):
     """Test handling of passing in the request uri."""
-    resp, content = fake_response('{',
+    resp, content = fake_response(b'{',
         {'status':'400', 'content-type': 'application/json'},
         reason='Failure')
     error = HttpError(resp, content, uri='http://example.org')
@@ -81,7 +81,7 @@
 
   def test_missing_message_json_body(self):
     """Test handling of bodies with missing expected 'message' element."""
-    resp, content = fake_response('{}',
+    resp, content = fake_response(b'{}',
         {'status':'400', 'content-type': 'application/json'},
         reason='Failed')
     error = HttpError(resp, content)
@@ -89,12 +89,12 @@
 
   def test_non_json(self):
     """Test handling of non-JSON bodies"""
-    resp, content = fake_response('}NOT OK', {'status':'400'})
+    resp, content = fake_response(b'}NOT OK', {'status':'400'})
     error = HttpError(resp, content)
     self.assertEqual(str(error), '<HttpError 400 "Ok">')
 
   def test_missing_reason(self):
     """Test an empty dict with a missing resp.reason."""
-    resp, content = fake_response('}NOT OK', {'status': '400'}, reason=None)
+    resp, content = fake_response(b'}NOT OK', {'status': '400'}, reason=None)
     error = HttpError(resp, content)
     self.assertEqual(str(error), '<HttpError 400 "">')
diff --git a/tests/test_http.py b/tests/test_http.py
index b47b9dc..d789630 100644
--- a/tests/test_http.py
+++ b/tests/test_http.py
@@ -460,7 +460,7 @@
 ETag: "etag/pony"\r\n\r\n{"answer": 42}"""
 
 
-BATCH_RESPONSE = """--batch_foobarbaz
+BATCH_RESPONSE = b"""--batch_foobarbaz
 Content-Type: application/http
 Content-Transfer-Encoding: binary
 Content-ID: <randomness+1>
@@ -482,7 +482,7 @@
 --batch_foobarbaz--"""
 
 
-BATCH_ERROR_RESPONSE = """--batch_foobarbaz
+BATCH_ERROR_RESPONSE = b"""--batch_foobarbaz
 Content-Type: application/http
 Content-Transfer-Encoding: binary
 Content-ID: <randomness+1>
@@ -518,7 +518,7 @@
 --batch_foobarbaz--"""
 
 
-BATCH_RESPONSE_WITH_401 = """--batch_foobarbaz
+BATCH_RESPONSE_WITH_401 = b"""--batch_foobarbaz
 Content-Type: application/http
 Content-Transfer-Encoding: binary
 Content-ID: <randomness+1>
@@ -541,7 +541,7 @@
 --batch_foobarbaz--"""
 
 
-BATCH_SINGLE_RESPONSE = """--batch_foobarbaz
+BATCH_SINGLE_RESPONSE = b"""--batch_foobarbaz
 Content-Type: application/http
 Content-Transfer-Encoding: binary
 Content-ID: <randomness+1>
@@ -928,7 +928,7 @@
 
     # Query parameters should be sent in the body.
     response = req.execute()
-    self.assertEqual('q=' + 'a' * MAX_URI_LENGTH + '%3F%26', response)
+    self.assertEqual(b'q=' + b'a' * MAX_URI_LENGTH + b'%3F%26', response)
 
     # Extra headers should be set.
     response = req.execute()
diff --git a/tests/test_json_model.py b/tests/test_json_model.py
index b198652..1784f8e 100644
--- a/tests/test_json_model.py
+++ b/tests/test_json_model.py
@@ -150,7 +150,7 @@
     model = JsonModel(data_wrapper=False)
     resp = httplib2.Response({'status': '401'})
     resp.reason = 'Unauthorized'
-    content = '{"error": {"message": "not authorized"}}'
+    content = b'{"error": {"message": "not authorized"}}'
 
     try:
       content = model.response(resp, content)
diff --git a/tests/test_mocks.py b/tests/test_mocks.py
index 6ccc427..a456b9e 100644
--- a/tests/test_mocks.py
+++ b/tests/test_mocks.py
@@ -134,7 +134,7 @@
   def test_errors(self):
     errorResponse = httplib2.Response({'status': 500, 'reason': 'Server Error'})
     requestBuilder = RequestMockBuilder({
-        'plus.activities.list': (errorResponse, '{}')
+        'plus.activities.list': (errorResponse, b'{}')
         })
     plus = build('plus', 'v1', http=self.http, requestBuilder=requestBuilder)
 
@@ -142,7 +142,7 @@
       activity = plus.activities().list(collection='public', userId='me').execute()
       self.fail('An exception should have been thrown')
     except HttpError as e:
-      self.assertEqual('{}', e.content)
+      self.assertEqual(b'{}', e.content)
       self.assertEqual(500, e.resp.status)
       self.assertEqual('Server Error', e.resp.reason)