diff --git a/Lib/multiprocessing/pool.py b/Lib/multiprocessing/pool.py
--- a/Lib/multiprocessing/pool.py
+++ b/Lib/multiprocessing/pool.py
@@ -275,6 +275,22 @@
         return self._map_async(func, iterable, starmapstar, chunksize,
                                callback, error_callback)
 
+    def _guarded_task_generation(self, result_job, func, iterable):
+        '''Provides a generator of tasks for imap and imap_unordered with
+        appropriate handling for iterables which throw exceptions during
+        iteration.'''
+        try:
+            i = -1
+            for i, x in enumerate(iterable):
+                yield (result_job, i, func, (x,), {})
+        except Exception as e:
+            yield (result_job, i+1, self._helper_reraises_exception, (e,), {})
+
+    @staticmethod
+    def _helper_reraises_exception(ex):
+        'Pickle-able helper function for use by _guarded_task_generation.'
+        raise ex
+
     def imap(self, func, iterable, chunksize=1):
         '''
         Equivalent of `map()` -- can be MUCH slower than `Pool.map()`.
@@ -283,15 +299,25 @@
             raise ValueError("Pool not running")
         if chunksize == 1:
             result = IMapIterator(self._cache)
-            self._taskqueue.put((((result._job, i, func, (x,), {})
-                         for i, x in enumerate(iterable)), result._set_length))
+            self._taskqueue.put(
+                (
+                    self._guarded_task_generation(result._job,
+                                                  func,
+                                                  iterable),
+                    result._set_length
+                ))
             return result
         else:
             assert chunksize > 1
             task_batches = Pool._get_tasks(func, iterable, chunksize)
             result = IMapIterator(self._cache)
-            self._taskqueue.put((((result._job, i, mapstar, (x,), {})
-                     for i, x in enumerate(task_batches)), result._set_length))
+            self._taskqueue.put(
+                (
+                    self._guarded_task_generation(result._job,
+                                                  mapstar,
+                                                  task_batches),
+                    result._set_length
+                ))
             return (item for chunk in result for item in chunk)
 
     def imap_unordered(self, func, iterable, chunksize=1):
@@ -302,15 +328,25 @@
             raise ValueError("Pool not running")
         if chunksize == 1:
             result = IMapUnorderedIterator(self._cache)
-            self._taskqueue.put((((result._job, i, func, (x,), {})
-                         for i, x in enumerate(iterable)), result._set_length))
+            self._taskqueue.put(
+                (
+                    self._guarded_task_generation(result._job,
+                                                  func,
+                                                  iterable),
+                    result._set_length
+                ))
             return result
         else:
             assert chunksize > 1
             task_batches = Pool._get_tasks(func, iterable, chunksize)
             result = IMapUnorderedIterator(self._cache)
-            self._taskqueue.put((((result._job, i, mapstar, (x,), {})
-                     for i, x in enumerate(task_batches)), result._set_length))
+            self._taskqueue.put(
+                (
+                    self._guarded_task_generation(result._job,
+                                                  mapstar,
+                                                  task_batches),
+                    result._set_length
+                ))
             return (item for chunk in result for item in chunk)
 
     def apply_async(self, func, args=(), kwds={}, callback=None,