But the vote was not unanimous with four Fine Gael councillors voting against it and the Lord Mayor, Naoise Ó Muirí, abstaining.
The motion, that “Dublin City Council supports full marriage equality for all citizens regardless of race, religion or sexuality” was tabled by Cllr Jane Horgan Jones (Lab), with a similar motion from a group led by Cllr Larry O’Toole (SF) passed at the same time.
Ms Horgan Jones said Dublin had an opportunity to show unanimous support for equality.
Cllr Kieran Binchy (FG) said he didn’t care if gay marriage was trendy, he would support the motion because it was “an idea whose time had come”.
And Mr O’Toole said that, as the largest council, Dublin needed to show a lead and recognise equal rights.
But Cllr Paddy McCartan (FG) said he wanted to put on the record there was not a consensus in the council.
He said he remembered when homosexuals and lesbians “were seen to be pariahs” and that was not correct.
But he did not see why there was a need to go beyond civil partnership.
Fine Gael councillor Dr Bill Tormey also voted against the motion.
He said the prime reason you can’t equate heterosexual and homosexual marriage was because the outcome was different, “it was children”.