diff --git a/docs/changelog.rst b/docs/changelog.rst
index f786c1d6..699c5a78 100644
--- a/docs/changelog.rst
+++ b/docs/changelog.rst
@@ -4,6 +4,7 @@ Changelog
 
 Changes in 0.8.X
 ================
+- Ensure as_pymongo() and to_json honour only() and exclude() (#293)
 - Document serialization uses field order to ensure a strict order is set (#296)
 - DecimalField now stores as float not string (#289)
 - UUIDField now stores as a binary by default (#292)
diff --git a/mongoengine/queryset/queryset.py b/mongoengine/queryset/queryset.py
index 65d6553f..5ae889c5 100644
--- a/mongoengine/queryset/queryset.py
+++ b/mongoengine/queryset/queryset.py
@@ -822,8 +822,7 @@ class QuerySet(object):
 
     def to_json(self):
         """Converts a queryset to JSON"""
-        queryset = self.clone()
-        return json_util.dumps(queryset._collection_obj.find(queryset._query))
+        return json_util.dumps(self.as_pymongo())
 
     def from_json(self, json_data):
         """Converts json data to unsaved objects"""
@@ -1095,7 +1094,7 @@ class QuerySet(object):
                 raise StopIteration
             if self._scalar:
                 return self._get_scalar(self._document._from_son(
-                        self._cursor.next()))
+                                        self._cursor.next()))
             if self._as_pymongo:
                 return self._get_as_pymongo(self._cursor.next())
 
@@ -1370,7 +1369,15 @@ class QuerySet(object):
                 new_data = {}
                 for key, value in data.iteritems():
                     new_path = '%s.%s' % (path, key) if path else key
-                    if all_fields or new_path in self.__as_pymongo_fields:
+
+                    if all_fields:
+                        include_field = True
+                    elif self._loaded_fields.value == QueryFieldList.ONLY:
+                        include_field = new_path in self.__as_pymongo_fields
+                    else:
+                        include_field = new_path not in self.__as_pymongo_fields
+
+                    if include_field:
                         new_data[key] = clean(value, path=new_path)
                 data = new_data
             elif isinstance(data, list):
diff --git a/tests/queryset/queryset.py b/tests/queryset/queryset.py
index 5e403c4e..5bf81835 100644
--- a/tests/queryset/queryset.py
+++ b/tests/queryset/queryset.py
@@ -3276,6 +3276,28 @@ class QuerySetTest(unittest.TestCase):
         self.assertEqual(results[1]['name'], 'Barack Obama')
         self.assertEqual(results[1]['price'], Decimal('2.22'))
 
+    def test_as_pymongo_json_limit_fields(self):
+
+        class User(Document):
+            email = EmailField(unique=True, required=True)
+            password_hash = StringField(db_field='password_hash', required=True)
+            password_salt = StringField(db_field='password_salt', required=True)
+
+        User.drop_collection()
+        User(email="ross@example.com", password_salt="SomeSalt", password_hash="SomeHash").save()
+
+        serialized_user = User.objects.exclude('password_salt', 'password_hash').as_pymongo()[0]
+        self.assertEqual(set(['_id', 'email']), set(serialized_user.keys()))
+
+        serialized_user = User.objects.exclude('id', 'password_salt', 'password_hash').to_json()
+        self.assertEqual('[{"email": "ross@example.com"}]', serialized_user)
+
+        serialized_user = User.objects.exclude('password_salt').only('email').as_pymongo()[0]
+        self.assertEqual(set(['email']), set(serialized_user.keys()))
+
+        serialized_user = User.objects.exclude('password_salt').only('email').to_json()
+        self.assertEqual('[{"email": "ross@example.com"}]', serialized_user)
+
     def test_no_dereference(self):
 
         class Organization(Document):