diff --git a/CHANGES/14064.bugfix.rst b/CHANGES/14064.bugfix.rst
new file mode 100644
index 00000000000..bdde8fe7891
--- /dev/null
+++ b/CHANGES/14064.bugfix.rst
@@ -0,0 +1,3 @@
+Fixed :class:`~aiohttp.CookieJar` keeping a cookie as a session cookie when its
+``Expires`` attribute is ``Thu, 01 Jan 1970 00:00:00 GMT``, instead of deleting
+it -- by :user:`spicysharkco`.
diff --git a/aiohttp/cookiejar.py b/aiohttp/cookiejar.py
index 12c781ce101..9f0462521e4 100644
--- a/aiohttp/cookiejar.py
+++ b/aiohttp/cookiejar.py
@@ -552,7 +552,7 @@ def _update_cookies(
                     cookie["max-age"] = ""
 
             elif expires := cookie["expires"]:
-                if expire_time := self._parse_date(expires):
+                if (expire_time := self._parse_date(expires)) is not None:
                     deadline = expire_time
                 else:
                     cookie["expires"] = ""
diff --git a/tests/test_cookiejar.py b/tests/test_cookiejar.py
index ed8f8525951..f78acafe788 100644
--- a/tests/test_cookiejar.py
+++ b/tests/test_cookiejar.py
@@ -1075,6 +1075,17 @@ async def test_cookie_jar_filter_cookies_expires() -> None:
     assert len(jar) == 0
 
 
+def test_cookie_jar_epoch_expires_deletes_cookie() -> None:
+    jar = CookieJar()
+    url = URL("https://example.com/")
+    jar.update_cookies_from_headers(["sid=old"], url)
+    jar.update_cookies_from_headers(
+        ["sid=; Expires=Thu, 01 Jan 1970 00:00:00 GMT"], url
+    )
+
+    assert len(jar.filter_cookies(url)) == 0
+
+
 async def test_cookie_jar_heap_cleanup() -> None:
     """Test that the heap gets cleaned up when there are many old expirations."""
     jar = CookieJar()