diff --git a/changelog.d/8644.misc b/changelog.d/8644.misc
new file mode 100644
index 000000000000..87f2b72924b2
--- /dev/null
+++ b/changelog.d/8644.misc
@@ -0,0 +1 @@
+Add field `total` to device list in admin API.
\ No newline at end of file
diff --git a/docs/admin_api/user_admin_api.rst b/docs/admin_api/user_admin_api.rst
index 7ca902faba25..0f3d99c82698 100644
--- a/docs/admin_api/user_admin_api.rst
+++ b/docs/admin_api/user_admin_api.rst
@@ -375,7 +375,8 @@ A response body like the following is returned:
           "last_seen_ts": 1474491775025,
           "user_id": "<user_id>"
         }
-      ]
+      ],
+      "total": 2
     }
 
 **Parameters**
@@ -400,6 +401,8 @@ The following fields are returned in the JSON response body:
     devices was last seen. (May be a few minutes out of date, for efficiency reasons).
   - ``user_id`` - Owner of  device.
 
+- ``total`` - Total number of user's devices.
+
 Delete multiple devices
 ------------------
 Deletes the given devices for a specific ``user_id``, and invalidates
diff --git a/synapse/rest/admin/devices.py b/synapse/rest/admin/devices.py
index a16386332205..ffd3aa38f768 100644
--- a/synapse/rest/admin/devices.py
+++ b/synapse/rest/admin/devices.py
@@ -119,7 +119,7 @@ async def on_GET(self, request, user_id):
             raise NotFoundError("Unknown user")
 
         devices = await self.device_handler.get_devices_by_user(target_user.to_string())
-        return 200, {"devices": devices}
+        return 200, {"devices": devices, "total": len(devices)}
 
 
 class DeleteDevicesRestServlet(RestServlet):
diff --git a/tests/rest/admin/test_device.py b/tests/rest/admin/test_device.py
index 92c9058887e2..d89eb90cfef5 100644
--- a/tests/rest/admin/test_device.py
+++ b/tests/rest/admin/test_device.py
@@ -393,6 +393,22 @@ def test_user_is_not_local(self):
         self.assertEqual(400, channel.code, msg=channel.json_body)
         self.assertEqual("Can only lookup local users", channel.json_body["error"])
 
+    def test_user_has_no_devices(self):
+        """
+        Tests that a normal lookup for devices is successfully
+        if user has no devices
+        """
+
+        # Get devices
+        request, channel = self.make_request(
+            "GET", self.url, access_token=self.admin_user_tok,
+        )
+        self.render(request)
+
+        self.assertEqual(200, channel.code, msg=channel.json_body)
+        self.assertEqual(0, channel.json_body["total"])
+        self.assertEqual(0, len(channel.json_body["devices"]))
+
     def test_get_devices(self):
         """
         Tests that a normal lookup for devices is successfully
@@ -409,6 +425,7 @@ def test_get_devices(self):
         self.render(request)
 
         self.assertEqual(200, channel.code, msg=channel.json_body)
+        self.assertEqual(number_devices, channel.json_body["total"])
         self.assertEqual(number_devices, len(channel.json_body["devices"]))
         self.assertEqual(self.other_user, channel.json_body["devices"][0]["user_id"])
         # Check that all fields are available