Thomas Taylor, 17, and two others were attacked close to Bedford bus station just before 6pm on Wednesday 8 January.
Bennett Ndenkeh, 19, produced a knife and fatally stabbed Thomas.
Emergency services were called to the scene in Greenhill Street and Thomas was taken to hospital, where he died shortly after arrival.
Ndenkeh was found guilty of murder following a seven-week trial at Luton Crown Court.
Riaz Miah, 18, was found not guilty of murder but convicted of manslaughter.
Detectives used CCTV to track the offenders, who dispersed minutes after the stabbing, and Ndenkeh and Miah were arrested within three days of the attack.
Miah told someone else who was at the altercation to “no comment everything” just hours before his arrest, messages on seized devices showed.
Two other teenagers were found not guilty of murder, while the jury was unable to reach a verdict on a fifth defendant.
During the trial, the court heard how Miah had been assaulted by someone linked to Thomas in the days before the stabbing.
On the day itself, Miah and Thomas exchanged messages, with Thomas warning against retaliation, before agreeing to meet in the town centre where the fatal altercation took place.
“This was a brutal and senseless act of violence that has ended the life of a young man who had so many years and experiences still in front of him and devasted the lives of those who knew him,” said Detective Chief Inspector Richard Stott from Bedfordshire Police.
“It has also drastically altered the path of the two people found guilty today – who are now facing the prospect of spending many of the prime years of their life behind bars.”
Ndenkeh and Miah will be sentenced on 10 October.
