diff --git a/CHANGES/7784.bugfix b/CHANGES/7784.bugfix
new file mode 100644
index 00000000000..1f8ba8ddb44
--- /dev/null
+++ b/CHANGES/7784.bugfix
@@ -0,0 +1 @@
+Fix duplicate cookie expiration calls in the CookieJar implementation
diff --git a/aiohttp/cookiejar.py b/aiohttp/cookiejar.py
index 87f05a0de3c..3c7629c7f33 100644
--- a/aiohttp/cookiejar.py
+++ b/aiohttp/cookiejar.py
@@ -154,7 +154,12 @@ def __iter__(self) -> "Iterator[Morsel[str]]":
             yield from val.values()
 
     def __len__(self) -> int:
-        return sum(1 for i in self)
+        """Return number of cookies.
+
+        This function does not iterate self to avoid unnecessary expiration
+        checks.
+        """
+        return sum(len(cookie.values()) for cookie in self._cookies.values())
 
     def _do_expiration(self) -> None:
         self.clear(lambda x: False)
diff --git a/tests/test_cookiejar.py b/tests/test_cookiejar.py
index 70ab0a4864e..261dbecd992 100644
--- a/tests/test_cookiejar.py
+++ b/tests/test_cookiejar.py
@@ -854,7 +854,28 @@ async def test_cookie_jar_clear_expired():
         assert len(sut) == 0
 
 
-async def test_cookie_jar_clear_domain():
+async def test_cookie_jar_filter_cookies_expires():
+    """Test that calling filter_cookies will expire stale cookies."""
+    jar = CookieJar()
+    assert len(jar) == 0
+
+    cookie = SimpleCookie()
+
+    cookie["foo"] = "bar"
+    cookie["foo"]["expires"] = "Tue, 1 Jan 1990 12:00:00 GMT"
+
+    with freeze_time("1980-01-01"):
+        jar.update_cookies(cookie)
+
+    assert len(jar) == 1
+
+    # filter_cookies should expire stale cookies
+    jar.filter_cookies(URL("http://any.com/"))
+
+    assert len(jar) == 0
+
+
+async def test_cookie_jar_clear_domain() -> None:
     sut = CookieJar()
     cookie = SimpleCookie()
     cookie["foo"] = "bar"