diff --git a/includes/class-admin-notices.php b/includes/admin/class-event-plugin-admin-notices.php
similarity index 91%
rename from includes/class-admin-notices.php
rename to includes/admin/class-event-plugin-admin-notices.php
index 5867458..9c0ba29 100644
--- a/includes/class-admin-notices.php
+++ b/includes/admin/class-event-plugin-admin-notices.php
@@ -1,6 +1,6 @@
 <?php
 /**
- * Class responsible for admin notices.
+ * Class responsible for Event Plugin related admin notices.
  *
  * Notices for guiding to proper configuration of ActivityPub with event plugins.
  *
@@ -8,16 +8,16 @@
  * @since 1.0.0
  */
 
-namespace Activitypub_Event_Extensions;
+namespace Activitypub_Event_Extensions\Admin;
 
 /**
- * Class Admin Notices.
+ * Class responsible for Event Plugin related admin notices.
  *
- * This class is responsible for admin notices.
+ * Notices for guiding to proper configuration of ActivityPub with event plugins.
  *
  * @since 1.0.0
  */
-class Admin_Notices {
+class Event_Plugin_Admin_Notices {
 	/**
 	 * Information about the event plugin.
 	 *
diff --git a/includes/admin/class-general-admin-notices.php b/includes/admin/class-general-admin-notices.php
new file mode 100644
index 0000000..7c12915
--- /dev/null
+++ b/includes/admin/class-general-admin-notices.php
@@ -0,0 +1,45 @@
+<?php
+/**
+ * Class responsible for Event Plugin related admin notices.
+ *
+ * Notices for guiding to proper configuration of ActivityPub with event plugins.
+ *
+ * @package Activitypub_Event_Extensions
+ * @since 1.0.0
+ */
+
+namespace Activitypub_Event_Extensions\Admin;
+
+/**
+ * Class responsible for Event Plugin related admin notices.
+ *
+ * Notices for guiding to proper configuration of ActivityPub with event plugins.
+ *
+ * @since 1.0.0
+ */
+class General_Admin_Notices {
+	/**
+	 * Warning if the plugin is Active and the ActivityPub plugin is not.
+	 */
+	public static function do_admin_notice_activitypub_plugin_not_enabled() {
+		$activitypub_plugin_url = 'https://wordpress.org/plugins/activitypub/';
+
+		$notice = sprintf(
+			/* translators: 1: the name of the event plugin a admin notice is shown. 2: The name of the ActivityPub plugin. */
+			_x(
+				'For the ActivityPub Event Extensions to work, you will need to install and activate the <a href="%1$s">ActivityPub</a> plugin.',
+				'admin notice',
+				'activitypub-event-extensions'
+			),
+			esc_html( $activitypub_plugin_url ),
+			admin_url( 'options-general.php?page=activitypub&tab=settings' )
+		);
+		$allowed_html = array(
+			'a' => array(
+				'href'  => true,
+				'title' => true,
+			),
+		);
+		echo '<div class="notice notice-warning"><p>' . \wp_kses( $notice, $allowed_html ) . '</p></div>';
+	}
+}
diff --git a/includes/class-setup.php b/includes/class-setup.php
index 56e6a27..088f6e5 100644
--- a/includes/class-setup.php
+++ b/includes/class-setup.php
@@ -11,6 +11,9 @@
 
 namespace Activitypub_Event_Extensions;
 
+use Activitypub_Event_Extensions\Admin\General_Admin_Notices;
+use Activitypub_Event_Extensions\Admin\Event_Plugin_Admin_Notices;
+
 // Exit if accessed directly.
 defined( 'ABSPATH' ) || exit; // @codeCoverageIgnore
 
@@ -51,6 +54,13 @@ class Setup {
 		),
 	);
 
+	/**
+	 * Keep the information whether the ActivityPub plugin is active.
+	 *
+	 * @var boolean
+	 */
+	protected $activitypub_plugin_is_active = false;
+
 	/**
 	 * Holds an array of the currently activated supported event plugins.
 	 *
@@ -66,10 +76,8 @@ class Setup {
 	 * @since 1.0.0
 	 */
 	protected function __construct() {
-		$this->active_event_plugins = self::detect_supported_event_plugins();
-		if ( empty( $this->active_event_plugins ) ) {
-			return;
-		}
+		$this->activitypub_plugin_is_active = is_plugin_active( 'activitypub/activitypub.php' );
+		$this->active_event_plugins         = self::detect_supported_event_plugins();
 		$this->setup_hooks();
 	}
 
@@ -127,6 +135,11 @@ class Setup {
 
 		add_action( 'admin_init', array( $this, 'do_admin_notices' ) );
 
+		// If we don't have any active event plugins, or the ActivityPub plugin is not enabled, abort here.
+		if ( empty( $this->active_event_plugins ) || ! $this->activitypub_plugin_is_active ) {
+			return;
+		}
+
 		add_filter( 'activitypub_transformer', array( $this, 'register_activitypub_event_transformer' ), 10, 3 );
 	}
 
@@ -135,7 +148,10 @@ class Setup {
 	 */
 	public function do_admin_notices(): void {
 		foreach ( $this->active_event_plugins as $event_plugin ) {
-			new Admin_Notices( $event_plugin );
+			new Event_Plugin_Admin_Notices( $event_plugin );
+		}
+		if ( ! $this->activitypub_plugin_is_active ) {
+			add_action( 'admin_notices', array( new General_Admin_Notices(), 'do_admin_notice_activitypub_plugin_not_enabled' ), 10, 1 );
 		}
 	}
 
@@ -177,13 +193,26 @@ class Setup {
 	 */
 	public function activate() {
 		// Don't allow plugin activation, when the ActivityPub plugin is not activated yet.
-		if ( ! is_plugin_active( 'activitypub/activitypub.php' ) ) {
+		if ( ! $this->activitypub_plugin_is_active ) {
 			deactivate_plugins( plugin_basename( ACTIVITYPUB_EVENT_EXTENSIONS_PLUGIN_FILE ) );
-			wp_die(
-				esc_html_e(
-					'Please install and activate the <a href="https://wordpress.org/plugins/activitypub/">ActivityPub plugin</a> first.',
-					'activitypub-event-extensions',
+			$notice = sprintf(
+				/* translators: 1: the name of the event plugin a admin notice is shown. 2: The name of the ActivityPub plugin. */
+				_x(
+					'To use this plugin install and activate the <a href="%1$s">%2$s</a> plugin first.',
+					'admin notice',
+					'activitypub-event-extensions'
 				),
+				esc_html( 'https://wordpress.org/plugins/activitypub' ),
+				esc_html( 'ActivityPub' )
+			);
+			$allowed_html = array(
+				'a' => array(
+					'href'  => true,
+					'title' => true,
+				),
+			);
+			wp_die(
+				wp_kses( $notice, $allowed_html ),
 				'Plugin dependency check',
 				array( 'back_link' => true ),
 			);