Green Party members will choose between Patricia McKenna and Minister for the Environment, John Gormley, TD, for the role of party leader.
The two candidates emerged from the contest for leadership of the party after nominations closed today.
As the sole candidate for the position of deputy leader, Mary White, TD for Carlow-Kilkenny, was re-elected by default.
Ballot papers will be sent by post to Green Party members on Monday, 9 July.
The deadline for return is Tuesday 17 July and the new leader will be announced that evening.