The Greens will elect a new female co-leader on April 8 to fill the position vacated by Metiria Turei last August.
Party co-leader James Shaw says nominations will open on February 2 and close a week later.
There is speculation Green MPs Marama Davidson, Julie Anne Genter, Eugenie Sage and Jan Logie will throw their hats into the ring.
Ms Davidson is tipped to announce her candidacy for the position on February 4, when she makes an announcement at Ngā Kete Wānanga Marae.
She's been tight-lipped about the specifics of the announcement and has previously not ruled out running for the position.
Despite not being a minister, Ms Davidson ranks second on the Green Party list (behind Mr Shaw), while Ms Genter, Ms Sage and Ms Logie all hold roles within Government.