Joe Gynane, 34, fatally injured Mohamed Elmi, 37, with a large kitchen knife in a “short but deadly assault” in the doorway of the Coach and Horses pub in Soho in the early hours of Sunday March 3.
Hours later, Gynane stabbed and seriously injured a 16-year-old boy in an alleyway off Tottenham Court Road.
Prosecutor Gareth Patterson QC told jurors: “A few months ago, on the morning of Sunday March 3, this defendant launched two violent knife attacks on the streets of this city.
“In his first knife attack he fatally stabbed a man called Mohamed Elmi in Soho.
“In a short but deadly assault in the doorway of a pub he stabbed him repeatedly using a large kitchen knife.”
Gynane and Mr Elmi had spent parts of the early morning together walking around Soho, smoking and taking drugs with a group of people, the court heard.
The defendant admitted he had taken heroin, crack cocaine and spice.
The court heard Gynane was a “dangerous” man with previous convictions for robbery and several assaults.
Gynane, of Wimbledon, south-west London, denied murder and causing grievous bodily harm with intent.
He claimed diminished responsibility on the basis he was suffering from “misuse syndrome” – the effects of the misuse of drugs – and a personality disorder.
A jury deliberated for three and a half hours to find him guilty of the charges.
Judge Richard Foster remanded the defendant into custody to be sentenced on Thursday afternoon.
Detective Inspector Justin Howick, from Scotland Yard, said: “Shortly after his arrest, Gynane admitted stabbing Mr Elmi and a second young man, in remorseless detail.
“His self-serving violence has had a terrible impact on Mr Elmi’s family, for whom this conviction will be of limited comfort.”