Kiffin was chosen Tuesday to replace Pete Carroll, his mentor and employer for six seasons. Kiffin was the Trojans' offensive coordinator before his brief stints with the Oakland Raiders and the Volunteers.
His father, respected defensive coach Monte Kiffin, and longtime USC assistant Ed Orgeron also will leave Tennessee to join him, USC said in a statement.
ESPN.com first reported the surprising move by Kiffin and the Trojans, who needed just one day to fill one of the most desirable jobs in college football. Carroll formally took over the Seattle Seahawks on Tuesday after winning 97 games over the past nine years.
"We are really excited to welcome Lane Kiffin back to USC," Trojans athletic director Mike Garrett said. "I was able to watch him closely when he was an assistant with us, and what I saw was a bright, creative young coach who I thought would make an excellent head coach here if the opportunity ever arose. I'm confident he and his staff will keep USC football performing at the high level that we expect."
The 34-year-old Kiffin is one of Carroll's top disciples from his nine-year tenure at USC. Kiffin, a former Fresno State quarterback, worked his way up to offensive coordinator in 2005 while also showing impressive recruiting skills.
For two seasons, he shared responsibility for the Trojans' offense with fellow longtime Carroll assistant Steve Sarkisian, who left USC to take over at Washington after the 2008 season.
Although Kiffin's forceful personality didn't make him a beloved figure among players or administrators, he was a key part of the Trojans' best years under Carroll, coordinating their passing game and providing instruction to quarterbacks Matt Leinart and John David Booty.
Kiffin then became Al Davis' unusual choice to take over the Oakland Raiders as a 31-year-old coach with almost no NFL experience. He made it through just 20 games before an ugly public firing in which Davis called Kiffin a liar who brought "disgrace" on the Raiders.
Kiffin went 7-6 at Tennessee last season as the youngest head coach in the Football Bowl Subdivision, but he also brought an unwelcome spotlight on the Vols with several minor NCAA violations.
He returns to USC with the school facing a yearslong NCAA investigation over events during his tenure as an assistant, including Reggie Bush's final years at the school.
Kiffin was suggested as a candidate immediately after Carroll's departure became official Sunday, but many Trojans thought he wouldn't be willing or able to leave Tennessee after just one year. Several coaches with USC ties said they weren't interested in the job, including NFL coaches Jeff Fisher and Jack Del Rio and Oregon State coach Mike Riley.
Monte Kiffin will lend his defensive acumen to a school that annually fielded an impressive defense under Carroll, while Orgeron is likely to return to his role as the Trojans' best recruiter who helped stack Carroll's early USC teams with a dizzying array of topflight talent.