The vote is the latest boost for Palestinian authorities campaigning for international recognition, coming after a similar vote by the British House of Commons and Sweden's decision to recognise a Palestinian state.
The motion yesterday called on the "government to formally recognise the state of Palestine and do everything it can to help secure a viable two-state solution to the Israeli-Palestinian conflict so that citizens of both states can live in peace and security."
Tabling the motion, opposition senator Averil Power said Ireland should "make it clear that statehood is a right of the Palestinian people and not a bargaining chip for the Israelis to play in further sham negotiations.
"In doing so, we will help increase pressure on Israel to pursue a genuine peace process that has a real prospect of delivering peace and justice for both Israelis and Palestinians alike."
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The Irish government is not bound to follow the motion, as it was initiated by an opposition lawmaker in the upper house, which has little real power.
"It was great that we didn't have to have a vote as we had cross-party support, which sends out a strong message," she said.
Ahead of the vote, the Israeli ambassador to Ireland Boaz Modai said he had contacted all senators to urge them to vote against the measure.
"Stunt gestures such as recognising 'Palestine' unilaterally are counter-productive because they only give excuses to those on the Palestinian side who hope to achieve their goals without talking directly to Israel," the embassy said in a statement.
The debate follows the collapse of peace talks between Israel and the Palestinian Authority and this year's conflict in Gaza in which more than 2,000 Palestinians and dozens of Israelis were killed.
According to an AFP count, at least 112 countries around the world have recognised a Palestinian state. A Palestinian count puts the number at 134.