Police called to an out-of control party in Hanworth discovered two revellers had been stabbed on Saturday night.
Officers were called at 12.30am on Sunday morning to break up a fight which had broken out at the private party in Uxbridge Road.
The first victim discovered was a 16-year-old girl who had been slashed across the face. She was taken by ambulance to a West London hospital and treated before being sent home.
Officers then noticed a man in his early twenties collapsed in nearby Hampton Road West. The second victim, who had also been stabbed was taken to a separate West London hospital where he remains in a serious but stable condition.
Officers from Hounslow CID, who are investigating the incidents, believe they both happened at the party which was being held in a domestic garage
Enquiries continue but no arrests have been made.