Police were called at approximately 6pm on Tuesday, 24 September to reports of a fight in the area West Lodge Avenue close to Ealing Common, W3.
Officers attended and found a man suffering from stab injuries. The London Ambulance Service and London’s Air Ambulance also attended.
The man, believed to be aged in his early 20s, was pronounced dead at the scene at 18:48hrs.
His next of kin have been informed.
A post-mortem examination will be held in due course.
Homicide detectives from Specialist Crime have been notified.
One person was arrested on suspicion of affray. He has been taken to a west London police station where he remains in custody.
A section 60 order has been implemented for the Hillingdon and Ealing areas and will be in place between 18:20hrs on Tuesday, 24 and 07:00hrs on Wednesday, 25 September.
Anyone with information is asked to call officers via 101 quoting reference Cad 5954/24Sep.