diff --git a/src/psrt_ghsa_bot/app.py b/src/psrt_ghsa_bot/app.py
index 60da65b..851d5e1 100644
--- a/src/psrt_ghsa_bot/app.py
+++ b/src/psrt_ghsa_bot/app.py
@@ -4,6 +4,7 @@
 import csv
 import datetime
 import os
+import re
 import typing
 
 import urllib3
@@ -101,6 +102,19 @@ def apply_to_repo(
 
         print(f"    📋 Processing {ghsa_id} (state: {state})")
 
+        # If the summary contains '[CLOSE]', '[CLOSED]', '[COMPLETE]',
+        # or '[COMPLETED]' then we can close the ticket.
+        summary = security_advisory.get("summary", "")
+        if re.search(r"\[(?:CLOSED?|COMPLETED?)\]", summary.upper()) is not None:
+            github.rest.security_advisories.update_repository_advisory(
+                owner=owner,
+                repo=repo,
+                ghsa_id=ghsa_id,
+                data={"state": "closed"},
+            )
+            print(f"    📋 Closed {ghsa_id}")
+            continue
+
         # Maintain a dictionary of updates to make and then submit them all at once.
         patch_data = {}
 
diff --git a/tests/test_app.py b/tests/test_app.py
index ac06c49..bb1d124 100644
--- a/tests/test_app.py
+++ b/tests/test_app.py
@@ -34,11 +34,12 @@ def cve_reserve_response(cve_id, year):
     }
 
 
-def _create_advisory_dict(state, cve_id, collaborating_teams):
+def _create_advisory_dict(state, cve_id, collaborating_teams, summary=""):
     """Helper to create a security advisory dictionary."""
     return {
         "ghsa_id": "GHSA-xxxx-xxxx-xxxx",
         "state": state,
+        "summary": summary,
         "cve_id": cve_id,
         "collaborating_teams": [{"slug": team} for team in collaborating_teams],
         "collaborating_users": [{"login": "octocat", "id": 1, "type": "User"}],
@@ -177,6 +178,35 @@ def test_update_collaborating_users() -> None:
     )
 
 
+@pytest.mark.parametrize(
+    "summary",
+    [
+        "[CLOSE] perl is better than Python",
+        "[CLOSED] 0.1 + 0.2 is broken?!?!?!?!?!",
+        "[COMPLETE] some boring security thing",
+        "fix soemthing in datetime module [COMPLETED]",
+        "blah blah [closed] lowercase blah",
+    ],
+)
+def test_closes_advisory_with_close_or_complete_tag(summary) -> None:
+    security_advisory = _create_advisory_dict("triage", None, [], summary=summary)
+
+    github = mock.Mock()
+    cve_api = mock.Mock()
+
+    with mock.patch("psrt_ghsa_bot.app.get_repository_advisories") as get_repo_advs:
+        get_repo_advs.return_value = [security_advisory]
+
+        app.apply_to_repo(github, "owner", "repo", cve_api)
+
+    github.rest.security_advisories.update_repository_advisory.assert_called_once_with(
+        owner="owner",
+        repo="repo",
+        ghsa_id="GHSA-xxxx-xxxx-xxxx",
+        data={"state": "closed"},
+    )
+
+
 def test_load_psrt_members_from_devguide() -> None:
     with mock.patch("psrt_ghsa_bot.app.urllib3.request") as urllib3_request:
         resp = mock.Mock()