diff -r bfd35f76fd0b Lib/test/test_csv.py
--- a/Lib/test/test_csv.py	Tue Jan 06 01:22:54 2015 +0100
+++ b/Lib/test/test_csv.py	Mon Jan 05 19:38:29 2015 -0800
@@ -1073,6 +1073,18 @@
             self.assertEqual(fileobj.read(), expected)
 
 
+class TestGenerator(unittest.TestCase):
+    def generator(self):
+        return (i for i in ['a', 'b', 'c'])
+
+    def test_generator_write(self):
+        with TemporaryFile('w+', newline='') as fileobj:
+            writer = csv.writer(fileobj)
+            writer.writerow(self.generator())
+            expected = ','.join(self.generator()) + '\r\n'
+            fileobj.seek(0)
+            self.assertEqual(fileobj.read(), expected)
+
 
 def test_main():
     mod = sys.modules[__name__]
diff -r bfd35f76fd0b Modules/_csv.c
--- a/Modules/_csv.c	Tue Jan 06 01:22:54 2015 +0100
+++ b/Modules/_csv.c	Mon Jan 05 19:38:29 2015 -0800
@@ -1193,12 +1193,18 @@
     Py_ssize_t len, i;
     PyObject *line, *result;
 
-    if (!PySequence_Check(seq))
+    if (PySequence_Check(seq))
+        Py_INCREF(seq);
+    else if (PyIter_Check(seq))
+        seq = PySequence_List(seq);
+    else
         return PyErr_Format(_csvstate_global->error_obj, "sequence expected");
 
     len = PySequence_Length(seq);
-    if (len < 0)
+    if (len < 0) {
+        Py_DECREF(seq);
         return NULL;
+    }
 
     /* Join all fields in internal buffer.
      */
@@ -1209,8 +1215,10 @@
         int quoted;
 
         field = PySequence_GetItem(seq, i);
-        if (field == NULL)
+        if (field == NULL) {
+            Py_DECREF(seq);
             return NULL;
+        }
 
         switch (dialect->quoting) {
         case QUOTE_NONNUMERIC:
@@ -1237,14 +1245,19 @@
 
             str = PyObject_Str(field);
             Py_DECREF(field);
-            if (str == NULL)
+            if (str == NULL) {
+                Py_DECREF(seq);
                 return NULL;
+            }
             append_ok = join_append(self, str, &quoted, len == 1);
             Py_DECREF(str);
         }
-        if (!append_ok)
+        if (!append_ok) {
+            Py_DECREF(seq);
             return NULL;
+        }
     }
+    Py_DECREF(seq);
 
     /* Add line terminator.
      */