The Steelers said Monday Tomlin would become the 16th head coach in the franchise's history. The Pittsburgh Post-Gazette had earlier reported that Tomlin had agreed to a four-year deal but other details were still being worked out.
Tomlin would replace Bill Cowher, who resigned this month after the team completed an 8-8 season and one year removed from a Super Bowl championship.
Tomlin, 34, spent one year with the Vikings after five seasons coaching defensive backs for Tampa Bay. He previously coached at four colleges.
The next coach at the Steelers will be just the third since 1969. Chuck Noll led the team for 23 years and Cowher was coach for 15.