diff --git a/projects/plugins/jetpack/changelog/fix-related-posts-warnings b/projects/plugins/jetpack/changelog/fix-related-posts-warnings
new file mode 100644
index 0000000000000..1ff52a765cb28
--- /dev/null
+++ b/projects/plugins/jetpack/changelog/fix-related-posts-warnings
@@ -0,0 +1,4 @@
+Significance: patch
+Type: other
+
+Related Posts: Prevent PHP errors when settings are malformed.
diff --git a/projects/plugins/jetpack/modules/related-posts/jetpack-related-posts.php b/projects/plugins/jetpack/modules/related-posts/jetpack-related-posts.php
index 292c4ec23d12a..c556eadee1915 100644
--- a/projects/plugins/jetpack/modules/related-posts/jetpack-related-posts.php
+++ b/projects/plugins/jetpack/modules/related-posts/jetpack-related-posts.php
@@ -198,7 +198,7 @@ public function action_frontend_init() {
 	public function get_headline() {
 		$options = $this->get_options();
 
-		if ( $options['show_headline'] ) {
+		if ( ! empty( $options['show_headline'] ) ) {
 			$headline = sprintf(
 				/** This filter is already documented in modules/sharedaddy/sharing-service.php */
 				apply_filters( 'jetpack_sharing_headline_html', '<h3 class="jp-relatedposts-headline"><em>%s</em></h3>', esc_html( $options['headline'] ), 'related-posts' ),
@@ -931,7 +931,7 @@ public function get_for_post_id( $post_id, array $args ) {
 		}
 
 		if (
-			! $options['enabled']
+			empty( $options['enabled'] )
 			|| 0 === (int) $post_id
 			|| empty( $options['size'] )
 		) {
@@ -1305,15 +1305,15 @@ protected function action_frontend_init_ajax( array $excludes ) {
 
 		$response = array(
 			'version'         => self::VERSION,
-			'show_thumbnails' => (bool) $options['show_thumbnails'],
-			'show_date'       => (bool) $options['show_date'],
-			'show_context'    => (bool) $options['show_context'],
-			'layout'          => (string) $options['layout'],
-			'headline'        => (string) $options['headline'],
+			'show_thumbnails' => (bool) ( $options['show_thumbnails'] ?? false ),
+			'show_date'       => (bool) ( $options['show_date'] ?? true ),
+			'show_context'    => (bool) ( $options['show_context'] ?? true ),
+			'layout'          => (string) ( $options['layout'] ?? 'grid' ),
+			'headline'        => (string) ( $options['headline'] ?? '' ),
 			'items'           => array(),
 		);
 
-		if ( count( $related_posts ) === $options['size'] ) {
+		if ( ! empty( $options['size'] ) && count( $related_posts ) === $options['size'] ) {
 			$response['items'] = $related_posts;
 		}