Police were called to Neasden Lane North, NW10 shortly after 21.30hrs on Monday, 11 January to reports of a disturbance.
Officers attended along with paramedics from London Ambulance Service (LAS) and London’s Air Ambulance.
A 48-year-old man was found with stab injuries. Despite the efforts of emergency services, he died at the scene.
The victim’s next of kin have been notified.
A 47-year-old man was found nearby suffering from non-life-threatening injuries. He was arrested in connection with the incident.
A 33-year-old man was also arrested later the same evening.
Both men were arrested on suspicion of murder.
One man remains in hospital receiving treatment to non-life-threatening injuries. A second remains in police custody.
Homicide detectives from the Met’s Specialist Crime Command investigate.
Detective Chief Inspector Tom Williams said: “The investigation is still in the early stages and we are appealing for any witnesses to come forward.
“How events unfolded remains unclear at the moment and we are keeping an open mind as to motive.
“Our team is working hard to capture as much evidence as possible in these crucial first stages and they are here to take your call. Please do not delay in making contact with us, even if you think the information you have is not important – it could prove crucial and may assist us in bringing whoever may be responsible to justice.”
A post-mortem examination is scheduled for Wednesday, 13 January.
Anyone with information should call police on 101 quoting 6783/11JAN.
To remain 100% anonymous please call Crimestoppers on 0800 555 111 or visit crimestoppers_uk.org.