The Western Kentucky position at the Bowling Green school came open when Willie Taggart left last week for the same role at South Florida.
Petrino was fired by the Razorbacks in April after revelations surfaced after a motorcycle crash that he had hired his mistress to a position in the football department and given her the equivalent of $20,000 in gifts.
Petrino had been in the middle of a seven-year contract under which his salary averaged $3.53 million per year.
Petrino was 34-17 in four seasons at Arkansas, leading the Razorbacks to a No. 5 final ranking last season and a Cotton Bowl win over Kansas State.
All that ended April 1, which Petrino at first described as a day spent with his wife at a northern Arkansas lake.
Instead, he and Jessica Dorrell went for a ride and skidded off the road in an accident that left him with four broken ribs, a cracked vertebra in his neck and numerous abrasions on his face. The avid motorcycle rider said the sun and wind had caused him to lose control on the two-lane highway about 20 miles southeast of Fayetteville.
What he failed to mention publicly was the presence of Dorrell.
That was revealed when a state police released an accident report. Petrino, tipped off by the state trooper who usually provides security for him during the season, informed Razorbacks athletic director Jeff Long of Dorrell's presence 20 minutes before police released the report to the public and admitted to what he called a previous inappropriate relationship with Dorrell.
Arkansas placed Petrino on paid leave that night, and he was eventually fired.
The coach's tenure with the Razorbacks began under a cloud of national second-guessing following his departure from the Atlanta Falcons 13 games into the 2007 season. His tenure with the Falcons was the shortest for a non-interim coach since the 1970 NFL-AFL merger.
"I love football. I love coaching," Petrino said after his firing by the Razorbacks. "I of course hope I can find my way back to the profession I love. In the meantime, I will do everything I can to heal the wounds I have created."