Chihab Saleh, 24 of Kilburn Square, Kilburn appeared at Harrow Crown Court on Thursday, 5 August.
He pleaded guilty to the manslaughter, by diminished responsibility, of 37-year-old Peter Petrou. He also pleaded guilty to possession of a bladed article.
Peter, who lived in West Kilburn, was killed on 16 July 2020.
The emergency services were called to Kilburn High Road following reports that a man had been stabbed.
Peter was taken to a central London hospital where he later died.
Saleh was arrested on 21 July 2020. He was charged with multiple offences, including murder, but a plea of manslaughter was subsequently accepted as above.
Detective Chief Inspector Perry Benton, from the Met’s Specialist Crime Command, said: “This is a tragic case that has left a family devastated. My thoughts remain with Peter’s family and friends as they come to terms with their grief.”