Police were called at around 8.54pm on Friday, 8 October, to a disturbance at residential premises in Hillingdon Road, Uxbridge.
Officers attended along with London Ambulance Service.
A 52-year-old man was taken to hospital. He was pronounced dead a short time later. A post-mortem examination will be arranged in due course and officers are in the process of informing the man’s family.
Enquiries continue to establish the circumstances. Two men and a woman were arrested at the address in connection with the incident. They have been taken into police custody.
Anyone with information or any witnesses are asked to call police on 101, ref 7960/08oct.