O'Brien is believed to be the first Roman Catholic bishop in U.S. history to be convicted of a felony.
The 68-year-old bishop, who said he thought he hit a dog or was struck by a rock, could be been sentenced to anywhere from probation to 3 3/4 years in prison on the charge of leaving the scene of an accident.
O'Brien, who appeared in court each day wearing a black shirt, Roman collar and a cross around his neck, showed no emotion after the verdict was read. He and his attorney left the courtroom without comment.
"It's a sad day," said Monsignor Dale Fushek, the diocese's co-vicar general and a friend of O'Brien. "It's the kind of situation where nobody wins. We respect the work the jury did, and now we just pray everyone heals."
Some members of the victim's family cried after the verdict, and members of the bishop's family declined to comment.
O'Brien led the Phoenix diocese's nearly 480,000 Catholics for 21 years, but stepped down in June after he was charged in the crash. O'Brien's successor scheduled an afternoon news conference to discuss the verdict.
The resignation came after two weeks of turmoil following an announcement by prosecutors that they had reached an immunity deal with O'Brien that would spare him indictment on obstruction charges for protecting priests accused of child molestation.
The chief facts surrounding the accident that killed pedestrian Jim Reed, 43, were not in dispute.
Reed was drunk and jaywalking on the night of June 14 when O'Brien hit him on his way home from celebrating Mass, leaving a giant spider-web crack in the windshield and Reed lying in the street. O'Brien then drove the two miles back to his house and parked the Buick in his garage.
The bishop, who testified for most of two days in the trial, said he heard a loud crash but never saw anyone in the road, and the defense contended that dim lighting, headlight glare and the victim's dark clothes made him hard to see.
Had he seen the pedestrian, O'Brien testified, "I would have stopped because that's the human thing to do. I couldn't imagine not stopping."
But prosecutors argued that O'Brien knew or should have known he hit a person. They pointed to the fact that O'Brien did not call police even after a official in the diocese told him the car may have been involved in a deadly accident.
They also noted that he tried to get the windshield repaired, even knowing police were looking for the car. Detectives tracked O'Brien down at his home two days after the accident.
"He goes ostrich. His head goes in the sand. Blinders are on. He just wants it to go away," prosecutor Anthony Novitsky said during closing arguments.
Authorities have said O'Brien would not have been charged with a crime if he had stopped and helped or, at the very least, waited for police to arrive.
Jurors deliberated about 4½ hours Friday and an additional two hours Tuesday before reaching their verdict. The case was initially given to the jury on Thursday, but deliberations had to start anew on Friday after one of the original jurors was dismissed and an alternate was substituted.
No sentencing date has been set.
The accident and O'Brien's abrupt resignation came just as it appeared he would survive as head of the diocese following a sex-abuse investigation.
As part of the deal with prosecutors, the bishop agreed that he would no longer handle abuse claims, but he refused to step down, saying it was the pope's decision whether to remove him and allow him to serve. He was allowed to resign after his arrest.
The clergy abuse investigation in the Phoenix diocese was one of several to rock the Roman Catholic church over the past two years.
By Ananda Shorey