diff --git a/core/lib/Drupal/Core/Template/Attribute.php b/core/lib/Drupal/Core/Template/Attribute.php
index 8aaac3b..0939ed3 100644
--- a/core/lib/Drupal/Core/Template/Attribute.php
+++ b/core/lib/Drupal/Core/Template/Attribute.php
@@ -240,6 +240,23 @@ public function removeAttribute() {
   }
 
   /**
+   * Merges the values of another Attributes object with this one.
+   *
+   * @param \Drupal\Core\Template\Attribute
+   *   The other Attribute object.
+   *
+   * @return $this
+   */
+  public function merge(Attribute $attribute) {
+    $merged_array = array_merge_recursive($this->toArray(), $attribute->toArray());
+    foreach ($merged_array as $attribute => $value) {
+      $this->setAttribute($attribute, $value);
+    }
+
+    return $this;
+  }
+
+  /**
    * Removes argument values from array of existing CSS classes.
    *
    * @param string|array ...
diff --git a/core/lib/Drupal/Core/Template/TwigSandboxPolicy.php b/core/lib/Drupal/Core/Template/TwigSandboxPolicy.php
index 5423bde..8f90dcf 100644
--- a/core/lib/Drupal/Core/Template/TwigSandboxPolicy.php
+++ b/core/lib/Drupal/Core/Template/TwigSandboxPolicy.php
@@ -57,6 +57,7 @@ public function __construct() {
       'bundle',
       'get',
       '__toString',
+      'merge',
     ]);
     $this->whitelisted_methods = array_flip($whitelisted_methods);
 
diff --git a/core/tests/Drupal/Tests/Core/Template/AttributeTest.php b/core/tests/Drupal/Tests/Core/Template/AttributeTest.php
index 69941a9..8510b89 100644
--- a/core/tests/Drupal/Tests/Core/Template/AttributeTest.php
+++ b/core/tests/Drupal/Tests/Core/Template/AttributeTest.php
@@ -145,6 +145,38 @@ public function testRemoveAttribute() {
   }
 
   /**
+   * Tests merging attributes.
+   * @covers ::merge
+   */
+  public function testMergeAttributes() {
+    $attributes1 = [
+      'id' => 'koala',
+      'class' => array('class1')
+    ];
+    $attribute1 = new Attribute($attributes1);
+
+    $attributes2 = [
+      'name' => 'pinguin',
+      'class' => array('class2', 'class3')
+    ];
+    $attribute2 = new Attribute($attributes2);
+
+    // Test merging another Attributes object
+    $attribute = new Attribute();
+    $attribute->merge($attribute1);
+    $this->assertArrayEquals(['class1'], $attribute['class']->value());
+    $this->assertEquals('koala', $attribute['id']->value());
+
+    // Test merging two Attributes object
+    $attribute = new Attribute();
+    $attribute->merge($attribute1);
+    $attribute->merge($attribute2);
+    $this->assertArrayEquals(['class1', 'class2', 'class3'], $attribute['class']->value());
+    $this->assertEquals('koala', $attribute['id']->value());
+    $this->assertEquals('pinguin', $attribute['name']->value());
+  }
+
+  /**
    * Tests adding class attributes with the AttributeArray helper method.
    * @covers ::addClass
    */