diff --git a/core/modules/block/custom_block/custom_block.pages.inc b/core/modules/block/custom_block/custom_block.pages.inc
index 9c802c4..a1e1144 100644
--- a/core/modules/block/custom_block/custom_block.pages.inc
+++ b/core/modules/block/custom_block/custom_block.pages.inc
@@ -99,6 +99,18 @@ function custom_block_delete_form($form, &$form_state, CustomBlock $block) {
     '#value' => $block->id(),
   );
 
+  $instances = entity_load_multiple_by_properties('block', array('plugin' => 'custom_block:' . $block->uuid->value));
+  if (!empty($instances)) {
+    $form['instances'] = array(
+      '#type' => 'value',
+      '#value' => $instances,
+    );
+    $form['message'] = array(
+      '#type' => 'markup',
+      '#markup' => format_plural(count($instances), 'This will also remove 1 placed block instance', 'This will also remove @count placed block instances'),
+    );
+  }
+
   return confirm_form(
     $form,
     t('Are you sure you want to delete %label?', array('%label' => $block->label())),
@@ -112,8 +124,11 @@ function custom_block_delete_form($form, &$form_state, CustomBlock $block) {
  * Form submission handler for custom_block_delete_form().
  */
 function custom_block_delete_form_submit($form, &$form_state) {
-  // @todo Delete all configured instances of the block.
   $block = $form_state['custom_block'];
+  $instances = $form_state['values']['instances'];
+  foreach ($instances as $instance) {
+    $instance->delete();
+  }
   $block->delete();
 
   drupal_set_message(t('Custom block %label has been deleted.', array('%label' => $block->label())));
diff --git a/core/modules/block/custom_block/lib/Drupal/custom_block/Tests/CustomBlockCreationTest.php b/core/modules/block/custom_block/lib/Drupal/custom_block/Tests/CustomBlockCreationTest.php
index c989682..6ada3c5 100644
--- a/core/modules/block/custom_block/lib/Drupal/custom_block/Tests/CustomBlockCreationTest.php
+++ b/core/modules/block/custom_block/lib/Drupal/custom_block/Tests/CustomBlockCreationTest.php
@@ -102,4 +102,49 @@ public function testFailedBlockCreation() {
       $this->assertTrue(count($records) > 0, 'Transactions not supported, and rollback error logged to watchdog.');
     }
   }
+
+  /**
+   * Test deleting a block.
+   */
+  public function testBlockDelete() {
+    // Create a block.
+    $edit = array();
+    $langcode = Language::LANGCODE_NOT_SPECIFIED;
+    $edit['info'] = $this->randomName(8);
+    $body = $this->randomName(16);
+    $edit["block_body[$langcode][0][value]"] = $body;
+    $this->drupalPost('block/add/basic', $edit, t('Save'));
+
+    // Place the block.
+    $instance = array(
+      'machine_name' => drupal_strtolower($edit['info']),
+      'settings[label]' => $edit['info'],
+      'region' => 'sidebar_first',
+    );
+    $this->drupalPost(NULL, $instance, t('Save block'));
+
+    $block = custom_block_load(1);
+
+    // Navigate to home page.
+    $this->drupalGet('');
+    $this->assertText($body);
+
+    // Delete the block.
+    $this->drupalGet('block/1/delete');
+    $this->assertText('This will also remove 1 placed block instance');
+
+    $this->drupalPost(NULL, array(), 'Delete');
+    $this->assertRaw(format_string('Custom block %name has been deleted.', array('%name' => $edit['info'])));
+
+    // Create another block and force the plugin cache to flush.
+    $edit2 = array();
+    $langcode = Language::LANGCODE_NOT_SPECIFIED;
+    $edit2['info'] = $this->randomName(8);
+    $body2 = $this->randomName(16);
+    $edit2["block_body[$langcode][0][value]"] = $body2;
+    $this->drupalPost('block/add/basic', $edit2, t('Save'));
+
+    $this->assertNoRaw('Error message');
+  }
+
 }