Party members have been voting for current leader Eamon Ryan, who has held the role since May 2011, and Catherine Martin, who has been deputy leader of the party since June 2011.
The deadline for the receipt of ballots for the leadership contest was 5.30pm on Wednesday.
Ballots were issued to 2,336 Green Party members in the Republic of Ireland, and to 598 Green Party members in Northern Ireland. The count will take place on Thursday with the result expected to be announced at 7pm.
Bids for leadership
Both candidates have been setting out their stalls in recent weeks in a bid to secure the leadership role.
Ms Martin told a previous hustings that she wanted to become leader to help the party achieve their goals in Government, adding that experience was not a “prerequisite” to becoming a leader.
After the Greens voted to go into Government, Ms Martin said that there was a “missed opportunity” by her party to promote women within its ranks to ministerial positions.
Ms Martin was also critical that Green TDs who opposed the Programme for Government document were excluded from the Cabinet table.
She said that while the party “talks the talk” on promoting diversity and inclusivity, it is not backing that up with action.
Ms Martin previously said: “I guess as a female pilot politician and someone who set up the caucus, I would always seek to promote women in our party.
But having said that, all Green Party ministers who are there are good for the job and I respect the decision there.”
Mr Ryan, meanwhile, used the hustings as an opportunity to focus on his experienced in government and as the Minister for Climate Action.
He said he wanted to remain as party leader, adding that his experience at the helm is important.
While the leader attracted some criticism when he appeared to be sleeping during a vote in the Dail last week, it is not expected to impact the final vote.
Once the vote has been declared, both candidates are expected to give a short speech.
