diff --git a/homeassistant/components/sia/utils.py b/homeassistant/components/sia/utils.py
index 66fdd7d95be..6b87c9cb1fc 100644
--- a/homeassistant/components/sia/utils.py
+++ b/homeassistant/components/sia/utils.py
@@ -6,6 +6,8 @@ from typing import Any
 
 from pysiaalarm import SIAEvent
 
+from homeassistant.util.dt import utcnow
+
 from .const import ATTR_CODE, ATTR_ID, ATTR_MESSAGE, ATTR_TIMESTAMP, ATTR_ZONE
 
 PING_INTERVAL_MARGIN = 30
@@ -42,7 +44,9 @@ def get_event_data_from_sia_event(event: SIAEvent) -> dict[str, Any]:
         "code": event.code,
         "message": event.message,
         "x_data": event.x_data,
-        "timestamp": event.timestamp.isoformat(),
+        "timestamp": event.timestamp.isoformat()
+        if event.timestamp
+        else utcnow().isoformat(),
         "event_qualifier": event.event_qualifier,
         "event_type": event.event_type,
         "partition": event.partition,