Police were called at approximately 18:30hrs on Monday, 29 June, to reports of a disturbance at a service road which runs at the rear of Ranelagh Road and Station Road, NW10.
Officers and London Ambulance Service attended the scene and found a man suffering serious stab injuries.
The man, believed to be in his early 50s, was pronounced dead at the scene.
Next have been informed. A post-mortem examination and formal identification will be held in due course.
A 29-year-old man was arrested at the scene on suspicion of murder. He has been taken to a north London police station where he remains in custody.
Officers from the Homicide and Major Crime Command (HMCC) are investigating.
Detective Chief Inspector Noel McHugh of the HMCC, who is leading the investigation, said: “I am appealing to anyone who may have been in the area as well as witnesses to the stabbing to contact us as soon as possible.
“They may hold vital information into what happened.”
Anyone who witnessed the incident or has information that may assist the investigation should call police on 0208 785 8099 or the police non-emergency line on 101.
To remain anonymous call Crimestoppers on 0800 555 111.