Police were called to Neasden Lane North, NW10 shortly after 9.30pm on Monday, 11 January to reports of a disturbance.
Officers attended along with paramedics from London Ambulance Service and London Air Ambulance.
A man, believed to be in his forties, was found with stab injuries.
Despite the efforts of emergency services, he died at the scene.
Efforts are ongoing to trace the man’s next of kin.
A second man- no further details- was also found with non life-threatening injuries nearby. He was arrested in connection with the incident.
Homicide detectives in the Met’s Specialist Crime Command have been informed.
A Section 60 has been authorised for the following wards areas: Barn Hill Hill, Welsh Harp, Tokyngton, Preston and Stonebridge from 10.30pm on Monday,11 January until 13.30hrs on Tuesday, 12 January.
A crime scene is in place.
Enquiries are ongoing.