Sahil Roy, 28, was pronounced dead near his housing estate in Isleworth last evening after emergency crew attempted to save his life for over an hour.
A Metropolitan Police statement said: "A murder investigation has been launched following the death of a man in Isleworth. Police were called at 4.05 PM (UK time) on Sunday to Summerwood Road in Isleworth following reports of man suffering from a stab injury.
"A post-mortem examination will be held in due course. Detectives from the Homicide and Major Crime Command (HMCC) are investigating."
A 22-year-old man has been arrested on suspicion of murder and is being held at a south London police station, the police confirmed.
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Roy is said to have been pushed to the ground and stabbed in the neck before his attackers fled.
Witnesses and friends told the 'Evening Standard' how the victim's mother sobbed by his side as she cradled him while he lay in the road.
One witness told the newspaper: "I just saw his mother with him in the road crying, holding his neck and head as he lay there in the road bleeding. It really was terrible."
Larissa Maher, a friend of Roy's, said: "He was an easily approachable person. He was really lovely. He wouldn't say boo to a ghost. We have a lot of bad people on the estate, but he wasn't one of them and you wouldn't expect it to be him.
"His brother came down and saw it as well, he must be going through hell. You can't feel safe around here. People just need to not carry knives around.