diff --git a/homeassistant/components/synology_dsm/config_flow.py b/homeassistant/components/synology_dsm/config_flow.py
index 0ddd22d3e1b..a4d7d75e073 100644
--- a/homeassistant/components/synology_dsm/config_flow.py
+++ b/homeassistant/components/synology_dsm/config_flow.py
@@ -179,11 +179,15 @@ class SynologyDSMFlowHandler(config_entries.ConfigFlow, domain=DOMAIN):
             discovery_info[ssdp.ATTR_UPNP_FRIENDLY_NAME].split("(", 1)[0].strip()
         )
 
+        mac = discovery_info[ssdp.ATTR_UPNP_SERIAL].upper()
         # Synology NAS can broadcast on multiple IP addresses, since they can be connected to multiple ethernets.
         # The serial of the NAS is actually its MAC address.
-        if self._mac_already_configured(discovery_info[ssdp.ATTR_UPNP_SERIAL].upper()):
+        if self._mac_already_configured(mac):
             return self.async_abort(reason="already_configured")
 
+        await self.async_set_unique_id(mac)
+        self._abort_if_unique_id_configured()
+
         self.discovered_conf = {
             CONF_NAME: friendly_name,
             CONF_HOST: parsed_url.hostname,
diff --git a/tests/components/synology_dsm/test_config_flow.py b/tests/components/synology_dsm/test_config_flow.py
index a339f015584..15a1655fbc1 100644
--- a/tests/components/synology_dsm/test_config_flow.py
+++ b/tests/components/synology_dsm/test_config_flow.py
@@ -385,6 +385,7 @@ async def test_form_ssdp(hass: HomeAssistantType, service: MagicMock):
     )
 
     assert result["type"] == data_entry_flow.RESULT_TYPE_CREATE_ENTRY
+    assert result["result"].unique_id == SERIAL
     assert result["title"] == "192.168.1.5"
     assert result["data"][CONF_HOST] == "192.168.1.5"
     assert result["data"][CONF_PORT] == 5001