diff --git a/shipitscript/src/shipitscript/data/mark_phase_as_completed_task_schema.json b/shipitscript/src/shipitscript/data/mark_phase_as_completed_task_schema.json
new file mode 100644
index 000000000..862ff8933
--- /dev/null
+++ b/shipitscript/src/shipitscript/data/mark_phase_as_completed_task_schema.json
@@ -0,0 +1,43 @@
+{
+    "title": "Taskcluster ShipIt mark-phase-as-completed task minimal schema",
+    "type": "object",
+    "properties": {
+        "dependencies": {
+            "type": "array",
+            "minItems": 1,
+            "uniqueItems": true,
+            "items": {
+                "type": "string"
+            }
+        },
+        "scopes": {
+            "type": "array",
+            "minItems": 2,
+            "uniqueItems": true,
+            "items": {
+                "type": "string"
+            }
+        },
+        "payload": {
+            "type": "object",
+            "properties": {
+                "release_name": {
+                    "type": "string"
+                },
+                "phase": {
+                    "type": "string"
+                }
+            },
+            "required": [
+                "release_name",
+                "phase"
+            ],
+            "additionalProperties": false
+        }
+    },
+    "required": [
+        "dependencies",
+        "scopes",
+        "payload"
+    ]
+}
\ No newline at end of file
diff --git a/shipitscript/src/shipitscript/script.py b/shipitscript/src/shipitscript/script.py
index e56a2ce5b..1cf432366 100644
--- a/shipitscript/src/shipitscript/script.py
+++ b/shipitscript/src/shipitscript/script.py
@@ -24,6 +24,16 @@ async def async_main(context):
     log.info("Success!")
 
 
+def mark_phase_as_completed_action(context):
+    """Action to perform is to tell Ship-it API that a phase can be marked
+    as completed"""
+    release_name = context.task["payload"]["release_name"]
+    phase = context.task["payload"]["phase"]
+
+    log.info("Marking the release's phase as completed ...")
+    ship_actions.mark_phase_as_completed(context.ship_it_instance_config, release_name, phase)
+
+
 def mark_as_shipped_action(context):
     """Action to perform is to tell Ship-it API that a release can be marked
     as shipped"""
@@ -63,7 +73,11 @@ def create_new_release_action(context):
 
 
 # ACTION_MAP {{{1
-ACTION_MAP = {"mark-as-shipped": mark_as_shipped_action, "create-new-release": create_new_release_action}
+ACTION_MAP = {
+    "mark-as-shipped": mark_as_shipped_action,
+    "create-new-release": create_new_release_action,
+    "mark-phase-as-completed": mark_phase_as_completed_action,
+}
 
 
 def get_default_config():
diff --git a/shipitscript/src/shipitscript/ship_actions.py b/shipitscript/src/shipitscript/ship_actions.py
index c17dc67d5..3d93a0330 100644
--- a/shipitscript/src/shipitscript/ship_actions.py
+++ b/shipitscript/src/shipitscript/ship_actions.py
@@ -102,3 +102,10 @@ def mark_as_shipped_v2(shipit_config, release_name):
     log.info("Marking the release as shipped...")
     release_api.update_status(release_name, status="shipped", headers=headers)
     check_release_has_values_v2(release_api, release_name, headers, status="shipped")
+
+
+def mark_phase_as_completed(shipit_config, release_name, phase):
+    release_api, headers = get_shipit_api_instance(shipit_config)
+
+    log.info("Marking the release's phase as completed ...")
+    release_api.update_phase_status(release_name, phase, status="completed", headers=headers)
diff --git a/shipitscript/src/shipitscript/shipitapi.py b/shipitscript/src/shipitscript/shipitapi.py
index 62e083f3b..560090066 100644
--- a/shipitscript/src/shipitscript/shipitapi.py
+++ b/shipitscript/src/shipitscript/shipitapi.py
@@ -150,3 +150,15 @@ def trigger_release_phase(self, release_name, phase, headers={}):
                 log.error(resp.content)
                 log.error(f"Response code: {resp.status_code}")
             raise
+
+    def update_phase_status(self, release_name, phase, status, headers={}):
+        data = json.dumps({"status": status})
+        response = None
+        try:
+            response = self._request(api_endpoint=f"/releases/{release_name}/{phase}", method="PATCH", data=data, headers=headers)
+        except Exception:
+            log.error(f"Caught error while triggering {phase} for {release_name}", exc_info=True)
+            if response:
+                log.error(response.content)
+                log.error(f"Response code: {response.status_code}")
+            raise