diff --git a/moto/swf/models/__init__.py b/moto/swf/models/__init__.py
index 622f38a02..5b4b96c87 100644
--- a/moto/swf/models/__init__.py
+++ b/moto/swf/models/__init__.py
@@ -191,6 +191,16 @@ class SWFBackend(BaseBackend):
         else:
             return None
 
+    def count_pending_decision_tasks(self, domain_name, task_list):
+        self._check_string(domain_name)
+        self._check_string(task_list)
+        domain = self._get_domain(domain_name)
+        count = 0
+        for _, wfe in domain.workflow_executions.iteritems():
+            if wfe.task_list == task_list:
+                count += wfe.open_counts["openDecisionTasks"]
+        return count
+
 
 swf_backends = {}
 for region in boto.swf.regions():
diff --git a/moto/swf/responses.py b/moto/swf/responses.py
index 8f8e86747..7832e3ebf 100644
--- a/moto/swf/responses.py
+++ b/moto/swf/responses.py
@@ -236,3 +236,9 @@ class SWFResponse(BaseResponse):
             )
         else:
             return json.dumps({"previousStartedEventId": 0, "startedEventId": 0})
+
+    def count_pending_decision_tasks(self):
+        domain_name = self._params["domain"]
+        task_list = self._params["taskList"]["name"]
+        count = self.swf_backend.count_pending_decision_tasks(domain_name, task_list)
+        return json.dumps({"count": count, "truncated": False})
diff --git a/tests/test_swf/test_decision_tasks.py b/tests/test_swf/test_decision_tasks.py
index 313736d7d..06cdd4556 100644
--- a/tests/test_swf/test_decision_tasks.py
+++ b/tests/test_swf/test_decision_tasks.py
@@ -57,3 +57,18 @@ def test_poll_for_decision_task_with_reverse_order():
     resp = conn.poll_for_decision_task("test-domain", "queue", reverse_order=True)
     types = [evt["eventType"] for evt in resp["events"]]
     types.should.equal(["DecisionTaskStarted", "DecisionTaskScheduled", "WorkflowExecutionStarted"])
+
+
+# CountPendingDecisionTasks endpoint
+@mock_swf
+def test_count_pending_decision_tasks():
+    conn = setup_workflow()
+    conn.poll_for_decision_task("test-domain", "queue")
+    resp = conn.count_pending_decision_tasks("test-domain", "queue")
+    resp.should.equal({"count": 1, "truncated": False})
+
+@mock_swf
+def test_count_pending_decision_tasks_on_non_existent_task_list():
+    conn = setup_workflow()
+    resp = conn.count_pending_decision_tasks("test-domain", "non-existent")
+    resp.should.equal({"count": 0, "truncated": False})