Before the vote, the Democratic Unionists tabled a “petition of concern” to ensure same-sex marriage could only be introduced if had cross-community support.
The motion won a majority of 50.5 per cent at Stormont, with all nationalist MLAs voting in favour and most unionists voting against.
It was the fifth time the assembly had debated the issue, and the first time it had voted in favour, and is being hailed as a symbolic victory by campaigners.
‘Failed to keep pace’
Patrick Corrigan, Amnesty’s programme director in Northern Ireland, said: “It shows that, slowly but surely, politicians are catching up with public opinion here, which has been in favour of equal marriage for same-sex couples for some years.
“However, the abuse of the petition of concern, to hold back rather than uphold the rights of a minority group, means that Stormont has once again failed to keep pace with equality legislation elsewhere in the UK and Ireland.”
Although Northern Ireland was the first part of the UK to allow same-sex civil partnerships in 2005, it is now the only part where civil marriage is denied to same-sex couples. It was signed into law in the Republic of Ireland last week.
While supporters of same-sex marriage say gay couples should have the same rights as heterosexuals, some Christian organisations in Northern Ireland argue that the institution of marriage should not be redefined.
In an open letter, Catholic bishops in Northern Ireland warned against a yes vote.
“Those who vote in favour of this motion have no way of knowing what the full consequences of such a vote will be,” they said.
“The truth about marriage derives from its intrinsic nature as a relationship based on the complementarity of a man and woman and the unique capacity of this relationship alone to generate new life. This truth does not change with the shifting tides of historical custom or popular opinion.”