The deal will keep Littrell with the Mean Green through the 2021 campaign.
"We are excited to announce this new agreement with coach Littrell," athletic director Wren Baker said. "Under one of the brightest young coaches in the country, our football program had the second-best turnaround in the nation last season and his performance was recognized by his colleagues and media members around the nation. This new contract represents an aggressive move to keep coach Littrell, his staff, and their positive momentum intact. This is validation of the successful efforts that Seth has led in the early stages of the turnaround of North Texas football."
Littrell inherited a 1-11 team last year, and managed to put together a five-win season in 2016.
"I am very grateful for the clear support from our Board of Regents, our president Neal Smatresk and our athletic director Wren Baker," Littrell said. "It means a lot to me to move forward with this new deal and continue to work hard with my staff to transform this into the championship-caliber program that our tremendous university, fans and alumni deserve."