diff --git a/src/Push/Push.php b/src/Push/Push.php
index 604854b..bc3f538 100644
--- a/src/Push/Push.php
+++ b/src/Push/Push.php
@@ -22,6 +22,11 @@ abstract class Push implements Request
      */
     protected $data = [];
 
+    /**
+     * @var string|null
+     */
+    protected $collapseKey = null;
+
     /**
      * @param string|array $iidToken
      * @return self
@@ -85,6 +90,18 @@ public function addData($name, $value): self
         return $this;
     }
 
+    /**
+     * @see https://firebase.google.com/docs/cloud-messaging/concept-options#collapsible_and_non-collapsible_messages
+     * @param string $collapseKey
+     *
+     * @return self
+     */
+    public function setCollapseKey(string $collapseKey): self
+    {
+        $this->collapseKey = $collapseKey;
+        return $this;
+    }
+
     /**
      * @inheritdoc
      */
@@ -126,6 +143,10 @@ public function buildJsonBody(): array
             $request['data'] = $this->data;
         }
 
+        if (!empty($this->collapseKey)) {
+            $request['collapse_key'] = $this->collapseKey;
+        }
+
         return $request;
     }
 }
diff --git a/tests/PushTests/DataTest.php b/tests/PushTests/DataTest.php
index fda7595..8d63894 100644
--- a/tests/PushTests/DataTest.php
+++ b/tests/PushTests/DataTest.php
@@ -121,6 +121,26 @@ public function it_can_generate_a_data_push_with_data()
         $this->assertEquals($expected, $data->buildJsonBody());
     }
 
+    /** @test */
+    public function it_can_generate_a_data_push_with_collapse_key()
+    {
+        $data = new \Fcm\Push\Data();
+        $data
+            ->addRecipient('device_1')
+            ->addData('key', 'value')
+            ->setCollapseKey('collapsekeyvalue');
+
+        $expected = [
+            'to' => 'device_1',
+            'data' => [
+                'key' => 'value',
+            ],
+            'collapse_key' => 'collapsekeyvalue',
+        ];
+
+        $this->assertEquals($expected, $data->buildJsonBody());
+    }
+
     /** @test */
     public function it_can_generate_a_quick_object_from_magic_method()
     {
diff --git a/tests/PushTests/NotificationTest.php b/tests/PushTests/NotificationTest.php
index 32a9242..d00cff6 100644
--- a/tests/PushTests/NotificationTest.php
+++ b/tests/PushTests/NotificationTest.php
@@ -284,6 +284,33 @@ public function it_can_generate_a_notification_with_add_data_array_twice()
         $this->assertEquals($expected, $notification->buildJsonBody());
     }
 
+    /** @test */
+    public function it_can_generate_a_notification_with_collapse_key()
+    {
+        $notification = new \Fcm\Push\Notification();
+        $notification
+            ->setTitle('Test title')
+            ->setBody('A small body as an example')
+            ->addRecipient('device_1')
+            ->setCollapseKey('collapsekeyvalue');
+
+        $expected = [
+            'to' => 'device_1',
+            'notification' => [
+                'title' => 'Test title',
+                'body'  => 'A small body as an example',
+                'sound'  => '',
+                'icon'  => '',
+                'color'  => '',
+                'tag'  => '',
+                'subtitle'  => '',
+            ],
+            'collapse_key' => 'collapsekeyvalue',
+        ];
+
+        $this->assertEquals($expected, $notification->buildJsonBody());
+        $this->assertSame('https://fcm.googleapis.com/fcm/send', $notification->getUrl());
+    }
 
     /** @test */
     public function it_can_generate_a_quick_object_from_magic_method()