Police were called at around 3.20am on Monday, 22 March, to a disturbance at premises in Granville Avenue, Hounslow.
Officers attended and found two men suffering from stab injuries.
A man, aged in his 20s, was treated at the scene by officers and paramedics, but he died at 4.23am
Police continue to work to inform next of kin.
The second man, also aged in his 20s, was taken to hospital but has since been discharged.
Enquiries continue to establish the circumstances.
There has been no arrest at this early stage.
Police have been conducting increased patrols in the Hounslow area to provide reassurance to the local community.
Detective Chief Inspector Vicky Tunstall, said: “I am appealing for witnesses who live within the vicinity of Granville Avenue, Hounslow or who may have been travelling through Granville Road at approximately 03:15hrs on Monday 22 March. Did you see any suspicious activity in this street involving several men in dark vehicles? Did you see three dark vehicles travelling together and away from the vicinity of number 9? We are also asking anyone with CCTV/Ring doorbell footage at your home or anyone with dash cam in your vehicle to contact police.
Any witnesses or anyone with any information is asked to call police on 101 Please quote CAD645/22MAR.