diff --git a/tests/phpunit/tests/admin/includes/ajax-actions/metaBoxOrder.php b/tests/phpunit/tests/admin/includes/ajax-actions/metaBoxOrder.php
new file mode 100644
index 0000000000000..dd1e2a499c6a6
--- /dev/null
+++ b/tests/phpunit/tests/admin/includes/ajax-actions/metaBoxOrder.php
@@ -0,0 +1,166 @@
+<?php
+
+/**
+ * Admin Ajax functions to be tested.
+ */
+require_once ABSPATH . 'wp-admin/includes/ajax-actions.php';
+
+/**
+ * Testing wp_ajax_meta_box_order() functionality.
+ *
+ * @package WordPress
+ * @subpackage UnitTests
+ * @since 3.1.0
+ *
+ * @group ajax
+ *
+ * @covers ::wp_ajax_meta_box_order
+ */
+class Tests_wp_ajax_meta_box_order extends WP_Ajax_UnitTestCase {
+
+	/**
+	 * Administrator user ID.
+	 *
+	 * @var int
+	 */
+	protected static $admin_id;
+
+	/**
+	 * Setup test fixtures.
+	 *
+	 * @param WP_UnitTest_Factory $factory
+	 */
+	public static function wpSetUpBeforeClass( WP_UnitTest_Factory $factory ): void {
+		self::$admin_id = $factory->user->create( array( 'role' => 'administrator' ) );
+	}
+
+	/**
+	 * Tests successful update of meta box order and page columns.
+	 *
+	 * @ticket 65252
+	 */
+	public function test_meta_box_order_success(): void {
+		wp_set_current_user( self::$admin_id );
+
+		$page  = 'testpage';
+		$order = array(
+			'side'     => 'box1,box2',
+			'normal'   => 'box3',
+			'advanced' => '',
+		);
+
+		$_POST = array(
+			'action'       => 'meta-box-order',
+			'_ajax_nonce'  => wp_create_nonce( 'meta-box-order' ),
+			'page'         => $page,
+			'order'        => $order,
+			'page_columns' => 2,
+		);
+
+		try {
+			$this->_handleAjax( 'meta-box-order' );
+		} catch ( WPAjaxDieContinueException $e ) {
+			// Expect success response via wp_send_json_success().
+		}
+
+		$response = json_decode( $this->_last_response, true );
+		$this->assertTrue( $response['success'] );
+
+		$saved_order = get_user_meta( self::$admin_id, "meta-box-order_$page", true );
+		$this->assertSame( $order, $saved_order );
+
+		$saved_columns = get_user_meta( self::$admin_id, "screen_layout_$page", true );
+		$this->assertSame( 2, (int) $saved_columns );
+	}
+
+	/**
+	 * Tests successful update with default page columns ('auto').
+	 *
+	 * @ticket 65252
+	 */
+	public function test_meta_box_order_auto_columns(): void {
+		wp_set_current_user( self::$admin_id );
+
+		$page = 'testpage_auto';
+
+		$_POST = array(
+			'action'       => 'meta-box-order',
+			'_ajax_nonce'  => wp_create_nonce( 'meta-box-order' ),
+			'page'         => $page,
+			'page_columns' => 'auto',
+		);
+
+		try {
+			$this->_handleAjax( 'meta-box-order' );
+		} catch ( WPAjaxDieContinueException $e ) {
+		}
+
+		$response = json_decode( $this->_last_response, true );
+		$this->assertTrue( $response['success'] );
+
+		$saved_columns = get_user_meta( self::$admin_id, "screen_layout_$page", true );
+		// In the code: if ( 'auto' !== $page_columns ) { $page_columns = (int) $page_columns; }
+		// Then update_user_meta( ..., $page_columns );
+		// Since 'auto' === 'auto', it remains 'auto'.
+		$this->assertSame( 'auto', $saved_columns );
+	}
+
+	/**
+	 * Tests failure due to invalid nonce.
+	 *
+	 * @ticket 65252
+	 */
+	public function test_meta_box_order_invalid_nonce(): void {
+		wp_set_current_user( self::$admin_id );
+
+		$_POST = array(
+			'action'      => 'meta-box-order',
+			'_ajax_nonce' => 'invalid-nonce',
+		);
+
+		$this->expectException( WPAjaxDieStopException::class );
+		$this->expectExceptionMessage( '-1' );
+
+		$this->_handleAjax( 'meta-box-order' );
+	}
+
+	/**
+	 * Tests failure due to invalid page parameter (fails sanitize_key).
+	 *
+	 * @ticket 65252
+	 */
+	public function test_meta_box_order_invalid_page(): void {
+		wp_set_current_user( self::$admin_id );
+
+		$_POST = array(
+			'action'      => 'meta-box-order',
+			'_ajax_nonce' => wp_create_nonce( 'meta-box-order' ),
+			'page'        => 'Invalid Page!', // Contains space and exclamation which sanitize_key removes.
+		);
+
+		$this->expectException( WPAjaxDieStopException::class );
+		$this->expectExceptionMessage( '0' );
+
+		$this->_handleAjax( 'meta-box-order' );
+	}
+
+	/**
+	 * Tests failure when no user is logged in.
+	 *
+	 * @ticket 65252
+	 */
+	public function test_meta_box_order_no_user(): void {
+		wp_set_current_user( 0 );
+
+		$_POST = array(
+			'action'      => 'meta-box-order',
+			'_ajax_nonce' => wp_create_nonce( 'meta-box-order' ),
+			'page'        => 'testpage',
+		);
+
+		$this->expectException( WPAjaxDieContinueException::class );
+		$this->expectExceptionMessage( '-1' );
+
+		$this->_handleAjax( 'meta-box-order' );
+	}
+}