Leavitt is expected to assist Seminoles defensive coordinator Harlon Barnett by bringing another experienced voice to help with devising game plans.
The Athletic first reported Leavitt would be joining Florida State’s staff in the off-the-field role of quality-control analyst.
Leavitt was Florida State coach Willie Taggart’s defensive coordinator in Taggart’s only season at Oregon in 2017.
Leavitt stayed behind when Taggart took the Seminoles job, hoping to land the head-coaching position at Oregon. But that went to Mario Cristobal. Leavitt remained the Ducks’ defensive coordinator last season, but parted ways with Cristobal after the season and has been out of college coaching since.
Leavitt was 95-57 in 13 seasons as the head coach at South Florida, building a fledgling program into a regular bowl participant. He was fired in 2009 after an investigation by the school found he grabbed and hit a player, and then misled school officials.
He landed in the NFL with the San Francisco 49ers before returning to college as defensive coordinator at Colorado under Mike MacIntyre in 2015. Leavitt helped turn around a struggling defense and the Buffs won the Pac-12 South in 2016.
Taggart hired Leavitt in 2017. After Taggart left Oregon, Leavitt was given a four-year contract that paid $1.7 million per season, making him one of the highest-paid coordinators in college football.
But the relationship between Cristobal and Leavitt was rocky, and Leavitt left Oregon earlier this year with a $2.5 million buyout.
Florida State (1-1) allowed 1,040 yards in its first two games, relinquishing double-digit leads in both. The Seminoles rank 83rd in the country in yards per play allowed (5.56) and 124th in yards per game (520.0).
The Associated Press contributed to this report.