Officers were called shortly before 10am in Saturday, 15 July to a residential address on Station Road in Hayes following reports of a man found deceased.
Officers and the London Ambulance Service attended. A man, aged in his mid-40s, was found with a slash wound; he pronounced dead the scene.
His family has been informed.
The death is currently being treated as unexpected and is under investigation.
A post-mortem examination will be held in due course.
At about 3.30am on Sunday, 16 July, officers arrested a man on suspicion of murder. He was taken to a west London police station where he remains in custody.
Enquiries continue.
