diff --git a/schedule/views.py b/schedule/views.py
index cef39c55..409b556f 100644
--- a/schedule/views.py
+++ b/schedule/views.py
@@ -327,20 +327,22 @@ def get_next_url(request, default):
 
 @check_calendar_permissions
 def api_occurrences(request):
-    start = request.GET.get("start")
-    end = request.GET.get("end")
-    calendar_slug = request.GET.get("calendar_slug")
-    timezone = request.GET.get("timezone")
+    start = request.GET.get('start')
+    end = request.GET.get('end')
+    timezone = request.GET.get('timezone')
+
+    calendar_slugs_raw = request.GET.get('calendar_slug')
+    calendar_slugs = calendar_slugs_raw.split(',') if calendar_slugs_raw else []
 
     try:
-        response_data = _api_occurrences(start, end, calendar_slug, timezone)
+        response_data = _api_occurrences(start, end, calendar_slugs, timezone)
     except (ValueError, Calendar.DoesNotExist) as e:
         return HttpResponseBadRequest(e)
 
     return JsonResponse(response_data, safe=False)
 
 
-def _api_occurrences(start, end, calendar_slug, timezone):
+def _api_occurrences(start, end, calendar_slugs, timezone):
 
     if not start or not end:
         raise ValueError("Start and end parameters are required")
@@ -376,9 +378,14 @@ def convert(ddatetime):
         start = utc.localize(start)
         end = utc.localize(end)
 
-    if calendar_slug:
+    if calendar_slugs:
         # will raise DoesNotExist exception if no match
-        calendars = [Calendar.objects.get(slug=calendar_slug)]
+        calendars = list(Calendar.objects.filter(slug__in=calendar_slugs))
+        missing_calendars = set(calendar_slugs) - set([s.slug for s in calendars])
+        if missing_calendars:
+            missing_msg = ", ".join("'{0}'".format(s) for s in missing_calendars)
+            msg = "Calendars {0} do not exist.".format(missing_msg)
+            raise Calendar.DoesNotExist(msg)
     # if no calendar slug is given, get all the calendars
     else:
         calendars = Calendar.objects.all()
diff --git a/tests/test_views.py b/tests/test_views.py
index 7254141f..f74b7818 100644
--- a/tests/test_views.py
+++ b/tests/test_views.py
@@ -580,6 +580,69 @@ def test_occurrences_api_fails_with_incorrect_date_string_formats(self):
         expected_error = "does not match format '%Y-%m-%dT%H:%M:%S'"
         self.assertIn(expected_error, resp)
 
+    def test_cal_multiple_slugs_return_all_events(self):
+        calendar1 = Calendar.objects.create(name="MyCal1", slug='MyCalSlug1')
+        calendar2 = Calendar.objects.create(name="MyCal2", slug='MyCalSlug2')
+        calendarOther = Calendar.objects.create(name="MyCalOther", slug='MyCalSlugOther')
+
+        event1 = Event.objects.create(
+            title='Recent Event 1',
+            start=datetime.datetime(2008, 1, 5, 8, 0, tzinfo=pytz.utc),
+            end=datetime.datetime(2008, 1, 5, 9, 0, tzinfo=pytz.utc),
+            end_recurring_period=datetime.datetime(2008, 5, 5, 0, 0, tzinfo=pytz.utc),
+            calendar=calendar1,
+        )
+        event2 = Event.objects.create(
+            title='Recent Event 2',
+            start=datetime.datetime(2008, 1, 5, 8, 0, tzinfo=pytz.utc),
+            end=datetime.datetime(2008, 1, 5, 9, 0, tzinfo=pytz.utc),
+            end_recurring_period=datetime.datetime(2008, 5, 5, 0, 0, tzinfo=pytz.utc),
+            calendar=calendar2,
+        )
+
+        eventOther = Event.objects.create(
+            title='Recent Event Other',
+            start=datetime.datetime(2008, 1, 5, 8, 0, tzinfo=pytz.utc),
+            end=datetime.datetime(2008, 1, 5, 9, 0, tzinfo=pytz.utc),
+            end_recurring_period=datetime.datetime(2008, 5, 5, 0, 0, tzinfo=pytz.utc),
+            calendar=calendarOther,
+        )
+
+        calendar_slug = ','.join(['MyCalSlug1', 'MyCalSlug2', ])
+
+        # Test both present with no cal arg
+        response = self.client.get(reverse("api_occurrences"),
+                                   {'start': '2008-01-05',
+                                    'end': '2008-02-05',
+                                    'calendar_slug': calendar_slug, }
+                                   )
+        self.assertEqual(response.status_code, 200)
+        resp_list = json.loads(response.content.decode('utf-8'))
+        self.assertIn(event1.title, [d['title'] for d in resp_list])
+        self.assertIn(event2.title, [d['title'] for d in resp_list])
+
+        self.assertNotIn(eventOther.title, [d['title'] for d in resp_list])
+
+    def test_cal_request_missing_returns_400(self):
+        calendar1 = Calendar.objects.create(name="MyCal1", slug='MyCalSlug1')
+
+        Event.objects.create(
+            title='Recent Event 1',
+            start=datetime.datetime(2008, 1, 5, 8, 0, tzinfo=pytz.utc),
+            end=datetime.datetime(2008, 1, 5, 9, 0, tzinfo=pytz.utc),
+            end_recurring_period=datetime.datetime(2008, 5, 5, 0, 0, tzinfo=pytz.utc),
+            calendar=calendar1,
+        )
+
+        calendar_slug = ','.join(['MyCalSlug1', 'MyCalSlugOther', ])
+        # Test both present with no cal arg
+        response = self.client.get(reverse("api_occurrences"),
+                                   {'start': '2008-01-05',
+                                    'end': '2008-02-05',
+                                    'calendar_slug': calendar_slug, }
+                                   )
+        self.assertContains(response, 'MyCalSlugOther', status_code=400)
+
     def test_check_next_url_valid_case(self):
         expected = "/calendar/1"
         res = check_next_url("/calendar/1")