if the exit polls are correct, it looks as if we will not have a majority," said secretary general Tom Curren, referring to his party's coalition with Labour.
The only possibilities of forming a government if the exit polls are correct would be a grand coalition or a coalition between the centre-right Fianna Fail party and Fine Gael.
This had been previously ruled out by outgoing Prime Minister Enda Kenny, whose leadership will now be questioned.
Exit polls conducted for national broadcaster RTE showed that Fine Gael received 24.8 per cent of first-preference votes, while Labour won 7.1 per cent. This is a sharp drop from the 2011 elections, when they received 36.1 per cent and 19.5 per cent respectively.
There were gains for opposition party Fianna Fail, which garned 21.1 per cent of the vote. The nationalist Sinn Fein party, previously known as the political wing of the IRA, is set to get 16 per cent, up 6 percentage points from 2011.
Independents and small parties, many of whom are left-wing, received 31 per cent of the vote, the poll suggests.
First unofficial results based on tallies at counts by party representatives are expected before midday.
Under Ireland's electoral system of proportional representation with a single transferable vote, counts can take a long time, and final official results may not be available until late Saturday.
More than 550 candidates are contesting 157 Dail seats in Ireland with some 3.1 million people eligible to vote.
Estimates put Friday's turnout at 65 per cent, down 5 per cent from the last general election in 2011.