Olivieri was facing first and third-degree murder charges.
Olivieri was 16 years old in October 2017, when he shot and killed DiNubile and Miller.
Assistant District Attorney David Osborne told the jury earlier this week that Olivieri, his friend Caleer Miller, and two others had been looking for a fight when they ran into Sal DiNubile and several others at 12th and Ritner streets.
Osborne said Olivieri had a gun tucked in his waistband.
Authorities allege Olivieri had been embarrassed in a previous fight and said when he saw DiNubile he stared him down and then pulled the weapon.
Osborne then told jurors DiNubile went for the gun in an effort to protect himself and his friends and was shot in the struggle. Osborne said Olivieri shot Miller by mistake.
Authorities said Olivieri then fled and both teens were pronounced dead.
Olivieri's defense attorney was outside court after the verdict came down.
"We did our best. It's a tragic case. Two young boys died and the third one is going to jail for a long, long time," said Robert Mozenter, the defendant's attorney.
The defense told the jury that the prosecution's case is based on inconsistency, chaos, and confusion, adding no gun was recovered and no forensic evidence links Olivieri to the crime.
However, on Friday the jury handed down the guilty verdict.
"We believe that justice has been served, but we'd really like to remind everyone that this is about the memories of the victims," said Matthew Krause, the prosecution's attorney.
Sal DiNubile's grandfather, Pat Bianculli, was outside of court after the verdict came down and said he believes justice had been served but he still misses his grandson everyday.
Sal DiNubile’s grandfather was outside of court after the verdict came down and says he believes justice has been served, but he still misses his grandson everyday, whose life was cut short at 16 years old. https://t.co/OvbILAlEPs @6abc pic.twitter.com/lZsTQk3G8M— Katie Katro (@KatieKatro6abc) May 17, 2019
"I believe justice was done, and I hope the sentencing is appropriate for the vicious crime he's committed," said Bianculli.
Olivieri will get 35 years to life for first degree murder, since he was a juvenile at the time.