Thirty-four-year-old Ohisalo, a poverty researcher and Helsinki city councillor, gained 11,000 votes in last month’s general election. The Greens are the fifth-largest party in Finland’s legislature after the Centre Party.
Last autumn two-time presidential candidate Pekka Haavisto was elected as the Green’s party chair after Touko Aalto announced he was stepping down from his party leadership position due to health reasons.
Haavisto said he would lead the party through April's parliamentary election but had no intention of continuing on as chair.
The party will officially select a new leader at its congress in Pori on 15 June.