25 returning from the 2016 season, two relegated from Ykkönen and nine promoted from Kolmonen.
The bottom three teams in each group will qualify directly for relegation to Kolmonen.
At the end of the season, a comparison is made between the runners-up.
Group winners and the best runner-up will play two-legged ties.
[1] Group winners The best runner-up Klubi 04 AC Kajaani won 6–3 on aggregate.