"We are privileged to have one of the top defensive coordinators in all of football in Bo Pelini join our staff," Tigers coach Ed Orgeron said in a statement. "Bo has had some of the best defenses in football during his career and we are looking forward to him bringing his tremendous amount of knowledge and expertise back to LSU to continue to win championships."
Pelini had confirmed the move in a statement posted Monday to his Twitter account, saying the "opportunity to return to LSU is truly unique."
"Culturally, with my prior experience at LSU, I know it is a great fit for me," Pelini said. "The chance to work with Coach Orgeron, the ability to take charge of the Tigers defense, is something that I'm extremely excited about."
He is receiving a multiyear contract with an annual salary comparable to Aranda's, which will make him one of college football's highest-paid assistants, sources told ESPN.
Pelini, who served as LSU's defensive coordinator from 2005 to 2007 and helped the Tigers to a national championship in 2007, has coached Youngstown State for the past five seasons. Pelini, 52, replaces Dave Aranda, who served as LSU's defensive coordinator the past four seasons before leaving for the head-coaching job at Baylor. Aranda had been the highest-paid assistant in college football, earning $2.5 million annually.
Pelini's son, Patrick, noted his father's return to LSU on Twitter.
Run it back! pic.twitter.com/Ac6PNmijnv— Patrick Pelini (@PPelini) January 27, 2020
Pelini is 100-55 as a head coach at Nebraska and Youngstown State. He has served as defensive coordinator at LSU, Oklahoma and Nebraska, and he coached linebackers for three NFL teams between 1994 and 2002.
After being fired by Nebraska following the 2014 season, Pelini returned to Youngstown, Ohio, his hometown, to coach the Penguins.
He guided Youngstown State to the FCS national championship game in his second season but did not win more than six games in any of the other four.
"The past five years have been terrific," Pelini said. "I can't thank President Jim Tressel and [athletic director] Ron Strollo enough for the opportunity here and support along the way. For all of the people, honestly too many to name, who were part of my YSU experience, I also want to extend a heartfelt thank you.
"The experience for me professionally to coach my hometown university and to appear in a championship game is something I will always treasure."