Mitchell was 8 of 11 from the field with 27 points. Tuttle was 6 of 9 from the field, with 21 points. He also had a team-high 10 rebounds. Marc Sonnen added 11 points for the Panthers (2-0).
Northern Iowa had a 41-38 lead at halftime, but Toledo was not done.
At the end of regulation, the score was tied at 70. Northern Iowa scored 14 points in overtime.
The game was the first-ever meeting between Northern Iowa and Toledo in basketball.
Toledo is a favorite to win the Mid-American Conference's West Division.
Alabama men's basketball head coach Avery Johnson joins The Paul Finebaum Show to discuss the importance of Cleveland's championship drought coming to an end.
Pirates catcher Jacob Stallings, the son of University of Pittsburgh basketball coach Kevin Stallings, made his major league debut on Sunday night.
Who made the biggest impact at the NBPA Top 100 camp? We update several top prospects such as Zion Williamson.