An NDP spokeswoman says a leadership contest is to be held March 9, 2013, in Saskatoon.
It will be help at the same time as the party's regular annual convention.
Anyone with a valid party membership will be allowed to vote online, by phone, with a mail-in ballot or in person.
Dwain Lingenfelter resigned after the election last fall when he lost his seat and the NDP dropped to nine seats in the 58-seat legislature.
Interim leader John Nilson has said he will not seek the job.
The official campaign period opens Sept. 4. The deadline to purchase memberships will be early next year.