The sovereigntist party must find a replacement Daniel Paille, who stepped down last month for health reasons.
The Bloc is looking to bounce back after a poor showing in the 2011 election and now has only four MPs in Ottawa.
The party says it will choose its new chief at a convention from May 23 to 25 in Rimouski, Que.
Details of the leadership race will be determined at a party meeting on Feb. 22.
So far, two Bloc MPs, Andre Bellavance et Jean-Francois Fortin, have shown interest in the post.