diff --git a/src/wp-includes/post.php b/src/wp-includes/post.php
index 509f63b9ab..aed2ee42f2 100644
--- a/src/wp-includes/post.php
+++ b/src/wp-includes/post.php
@@ -3090,14 +3090,24 @@ function wp_count_posts( $type = 'post', $perm = '' ) {
 function wp_count_attachments( $mime_type = '' ) {
 	global $wpdb;
 
-	$and   = wp_post_mime_type_where( $mime_type );
-	$count = $wpdb->get_results( "SELECT post_mime_type, COUNT( * ) AS num_posts FROM $wpdb->posts WHERE post_type = 'attachment' AND post_status != 'trash' $and GROUP BY post_mime_type", ARRAY_A );
+	$cache_key = sprintf(
+		'attachments%s',
+		! empty( $mime_type ) ? ':' . str_replace( '/', '_', implode( '-', (array) $mime_type ) ) : ''
+	);
 
-	$counts = array();
-	foreach ( (array) $count as $row ) {
-		$counts[ $row['post_mime_type'] ] = $row['num_posts'];
+	$counts = wp_cache_get( $cache_key, 'counts' );
+	if ( false == $counts ) {
+		$and   = wp_post_mime_type_where( $mime_type );
+		$count = $wpdb->get_results( "SELECT post_mime_type, COUNT( * ) AS num_posts FROM $wpdb->posts WHERE post_type = 'attachment' AND post_status != 'trash' $and GROUP BY post_mime_type", ARRAY_A );
+
+		$counts = array();
+		foreach ( (array) $count as $row ) {
+			$counts[ $row['post_mime_type'] ] = $row['num_posts'];
+		}
+		$counts['trash'] = $wpdb->get_var( "SELECT COUNT( * ) FROM $wpdb->posts WHERE post_type = 'attachment' AND post_status = 'trash' $and" );
+
+		wp_cache_set( $cache_key, (object) $counts, 'counts' );
 	}
-	$counts['trash'] = $wpdb->get_var( "SELECT COUNT( * ) FROM $wpdb->posts WHERE post_type = 'attachment' AND post_status = 'trash' $and" );
 
 	/**
 	 * Modifies returned attachment counts by mime type.
diff --git a/tests/phpunit/tests/post/wpCountAttachments.php b/tests/phpunit/tests/post/wpCountAttachments.php
new file mode 100644
index 0000000000..af895d3a7b
--- /dev/null
+++ b/tests/phpunit/tests/post/wpCountAttachments.php
@@ -0,0 +1,33 @@
+<?php
+
+/**
+ * @group post
+ * @group media
+ * @group upload
+ *
+ * @covers ::wp_count_attachments
+ */
+class Tests_Post_wpCountAttachments extends WP_UnitTestCase {
+
+	/**
+	 * Tests that the result is cached.
+	 *
+	 * @ticket 55227
+	 */
+	public function test_wp_count_attachments_should_cache_the_result() {
+		$mime_type = 'image/jpeg';
+		$cache_key = 'attachments:image_jpeg';
+
+		self::factory()->post->create_many(
+			3,
+			array(
+				'post_type'      => 'attachment',
+				'post_mime_type' => $mime_type,
+			)
+		);
+		$expected = wp_count_attachments( $mime_type );
+		$actual   = wp_cache_get( $cache_key, 'counts' );
+
+		$this->assertEquals( $expected, $actual );
+	}
+}