diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index f29da0e3f1..e6ac1bff52 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -24,6 +24,8 @@ Added
   values - ``succeeded`` (trigger instance matched a rule and action execution was triggered
   successfully), ``failed`` (trigger instance matched a rule, but it didn't result in an action
   execution due to Jinja rendering failure or other exception). (improvement) #4134
+* Add trigger type reference based filtering to the ``/v1/triggerinstances`` API endpoint - e.g.
+  ``/v1/triggerinstances?trigger_type=core.st2.webhook``. (new feature) #4151
 
 Changed
 ~~~~~~~
diff --git a/st2api/st2api/controllers/resource.py b/st2api/st2api/controllers/resource.py
index df1f174219..c2040f5c7d 100644
--- a/st2api/st2api/controllers/resource.py
+++ b/st2api/st2api/controllers/resource.py
@@ -181,7 +181,13 @@ def _get_all(self, exclude_fields=None, include_fields=None, advanced_filters=No
             if k in ['id', 'name'] and isinstance(filter_value, list):
                 filters[k + '__in'] = filter_value
             else:
-                filters['__'.join(v.split('.'))] = filter_value
+                field_name_split = v.split('.')
+
+                # Make sure filter value is a list when using "in" filter
+                if field_name_split[-1] == 'in' and not isinstance(filter_value, (list, tuple)):
+                    filter_value = [filter_value]
+
+                filters['__'.join(field_name_split)] = filter_value
 
         if advanced_filters:
             for token in advanced_filters.split(' '):
diff --git a/st2api/st2api/controllers/v1/triggers.py b/st2api/st2api/controllers/v1/triggers.py
index 84d2d3700d..847aade2b5 100644
--- a/st2api/st2api/controllers/v1/triggers.py
+++ b/st2api/st2api/controllers/v1/triggers.py
@@ -359,10 +359,10 @@ class TriggerInstanceController(TriggerInstanceControllerMixin, resource.Resourc
         the lifecycle of TriggerInstances in the system.
     """
     supported_filters = {
-        'trigger': 'trigger',
         'timestamp_gt': 'occurrence_time.gt',
         'timestamp_lt': 'occurrence_time.lt',
-        'status': 'status'
+        'status': 'status',
+        'trigger': 'trigger.in'
     }
 
     filter_transform_functions = {
@@ -393,6 +393,21 @@ def get_all(self, sort=None, offset=0, limit=None, requester_user=None, **raw_fi
             Handles requests:
                 GET /triggerinstances/
         """
+        # If trigger_type filter is provided, filter based on the TriggerType via Trigger object
+        trigger_type_ref = raw_filters.get('trigger_type', None)
+
+        if trigger_type_ref:
+            # 1. Retrieve TriggerType object id which match this trigger_type ref
+            trigger_dbs = Trigger.query(type=trigger_type_ref,
+                                        only_fields=['ref', 'name', 'pack', 'type'])
+            trigger_refs = [trigger_db.ref for trigger_db in trigger_dbs]
+            raw_filters['trigger'] = trigger_refs
+
+        if trigger_type_ref and len(raw_filters.get('trigger', [])) == 0:
+            # Empty list means trigger_type_ref filter was provided, but we matched no Triggers so
+            # we should return back empty result
+            return []
+
         trigger_instances = self._get_trigger_instances(sort=sort,
                                                         offset=offset,
                                                         limit=limit,
diff --git a/st2api/tests/unit/controllers/v1/test_triggerinstances.py b/st2api/tests/unit/controllers/v1/test_triggerinstances.py
index 814db3ce4a..b796b0a6e3 100644
--- a/st2api/tests/unit/controllers/v1/test_triggerinstances.py
+++ b/st2api/tests/unit/controllers/v1/test_triggerinstances.py
@@ -73,6 +73,22 @@ def test_get_all_filter_by_timestamp(self):
         resp = self.app.get('/v1/triggerinstances?timestamp_lt=%s' % (timestamp_middle))
         self.assertEqual(len(resp.json), 1)
 
+    def test_get_all_trigger_type_ref_filtering(self):
+        # 1. Invalid / inexistent trigger type ref
+        resp = self.app.get('/v1/triggerinstances?trigger_type=foo.bar.invalid')
+        self.assertEqual(resp.status_int, http_client.OK)
+        self.assertEqual(len(resp.json), 0)
+
+        # 2. Valid trigger type ref with corresponding trigger instances
+        resp = self.app.get('/v1/triggerinstances?trigger_type=dummy_pack_1.st2.test.triggertype0')
+        self.assertEqual(resp.status_int, http_client.OK)
+        self.assertEqual(len(resp.json), 1)
+
+        # 3. Valid trigger type ref with no corresponding trigger instances
+        resp = self.app.get('/v1/triggerinstances?trigger_type=dummy_pack_1.st2.test.triggertype3')
+        self.assertEqual(resp.status_int, http_client.OK)
+        self.assertEqual(len(resp.json), 0)
+
     def test_reemit_trigger_instance(self):
         resp = self.app.get('/v1/triggerinstances')
         self.assertEqual(resp.status_int, http_client.OK)
@@ -127,9 +143,17 @@ def _setupTriggerTypes(cls):
             'payload_schema': {'tp1': None, 'tp2': None, 'tp3': None},
             'parameters_schema': {'param1': {'type': 'object'}}
         }
+        TRIGGERTYPE_3 = {
+            'name': 'st2.test.triggertype3',
+            'pack': 'dummy_pack_1',
+            'description': 'test trigger',
+            'payload_schema': {'tp1': None, 'tp2': None, 'tp3': None},
+            'parameters_schema': {'param1': {'type': 'object'}}
+        }
         cls.app.post_json('/v1/triggertypes', TRIGGERTYPE_0, expect_errors=False)
         cls.app.post_json('/v1/triggertypes', TRIGGERTYPE_1, expect_errors=False)
         cls.app.post_json('/v1/triggertypes', TRIGGERTYPE_2, expect_errors=False)
+        cls.app.post_json('/v1/triggertypes', TRIGGERTYPE_3, expect_errors=False)
 
     @classmethod
     def _setupTriggers(cls):
diff --git a/st2common/st2common/openapi.yaml b/st2common/st2common/openapi.yaml
index 01235e7aa4..4413ebd1a7 100644
--- a/st2common/st2common/openapi.yaml
+++ b/st2common/st2common/openapi.yaml
@@ -3918,6 +3918,10 @@ paths:
           description: Start timestamp greater than filter
           type: string
           pattern: ^\d{4}\-\d{2}\-\d{2}(\s|T)\d{2}:\d{2}:\d{2}(\.\d{3,6})?(Z|\+00|\+0000|\+00:00)$
+        - name: trigger_type
+          in: query
+          description: Trigger type filter
+          type: string
       x-parameters:
         - name: user
           in: context
diff --git a/st2common/st2common/openapi.yaml.j2 b/st2common/st2common/openapi.yaml.j2
index b3ff5d631a..59d5202754 100644
--- a/st2common/st2common/openapi.yaml.j2
+++ b/st2common/st2common/openapi.yaml.j2
@@ -3914,6 +3914,10 @@ paths:
           description: Start timestamp greater than filter
           type: string
           pattern: {{ ISO8601_UTC_REGEX }}
+        - name: trigger_type
+          in: query
+          description: Trigger type filter
+          type: string
       x-parameters:
         - name: user
           in: context