diff --git a/admin-notice/admin-notice.php b/admin-notice/admin-notice.php
index 3b84c5ade6..bf29887071 100644
--- a/admin-notice/admin-notice.php
+++ b/admin-notice/admin-notice.php
@@ -26,3 +26,20 @@ function () use ( $admin_notice_controller ) {
 		do_action( 'vip_admin_notice_init', $admin_notice_controller );
 	}
 );
+
+add_action(
+	'vip_admin_notice_init',
+	function ( $admin_notice_controller ) {
+		$message = 'Heads up! Your site is using a deprecated plugin <a href="https://github.com/Automattic/jetpack-force-2fa/">jetpack-force-2fa</a>. This functionality is already included in Jetpack as of version 13.5. Please remove the plugin to avoid potential conflicts with future Jetpack updates.';
+		$admin_notice_controller->add(
+			new Admin_Notice(
+				$message,
+				[
+					new Expression_Condition( class_exists( 'Jetpack_Force_2FA' ) && class_exists( 'Jetpack' ) && defined( 'JETPACK__VERSION' ) && version_compare( JETPACK__VERSION, '13.5', '>=' ) ),
+				],
+				'deprecated-standalone-jetpack-2fa-plugin',
+				'error'
+			)
+		);
+	}
+);
diff --git a/vip-jetpack/jetpack-sso-dummy.php b/vip-jetpack/jetpack-sso-dummy.php
new file mode 100644
index 0000000000..94c8114a66
--- /dev/null
+++ b/vip-jetpack/jetpack-sso-dummy.php
@@ -0,0 +1,7 @@
+<?php
+
+if ( ! class_exists( '\Automattic\Jetpack\Connection\SSO' ) ) {
+	return;
+}
+
+class Jetpack_SSO extends \Automattic\Jetpack\Connection\SSO {}
diff --git a/vip-jetpack/vip-jetpack.php b/vip-jetpack/vip-jetpack.php
index 8c9e737816..64ea9e70b5 100644
--- a/vip-jetpack/vip-jetpack.php
+++ b/vip-jetpack/vip-jetpack.php
@@ -434,3 +434,15 @@ function vip_prevent_jetpack_post_by_email_database_noise() {
 		unset( $_POST['invite_user_wpcom'] );
 	}
 });
+
+/**
+ * Jetpack 13.9 removes the legacy Jetpack_SSO class. Unfortunately, this class is still used by
+ * the deprecated standalone jetpack-force-2fa plugin (which is still in use by some). This is a dummy
+ * class to prevent fatal errors when the standalone plugin is enabled.
+ */
+add_action( 'plugins_loaded', function () {
+	if ( class_exists( 'Jetpack_Force_2FA' ) && ! class_exists( 'Jetpack_SSO' ) && class_exists( 'Jetpack' ) &&
+		defined( 'JETPACK__VERSION' ) && version_compare( JETPACK__VERSION, '13.9', '>=' ) ) {
+		require_once __DIR__ . '/jetpack-sso-dummy.php';
+	}
+} );