Same-sex marriage campaigners say the overwhelming support for the bill at its second hurdle is a ringing endorsement which shows MPs are in line with the views of ordinary New Zealanders.
Labour MP Louisa Wall's bill passed its second reading last night 77 votes to 44, a drop in support of three votes from the first reading.
Campaign for Marriage Equality spokesman Conrad Reyners said the vote was a second ringing endorsement for marriage equality.
"Parliament has listened to the voices of thousands of New Zealanders, many of who explained how positive and important this change was for their dignity and their lives."
Mr Reyners said the debate had been controversial, and he recognised the depth of feeling on all sides.
"We are proud to see Parliament voting with the majority of ordinary kiwis, who know marriage is about love, family and commitment," he said.
"This vote is another step forward for love, for fairness and for equal treatment before the law.''
Conservative lobby group Family First this morning said it would continue to oppose the bill.
"It is hugely concerning that the politicians failed to grasp some critical consequences of changing the definition of marriage," national director Bob McCoskrie said.
He said there was almost no discussion at the second reading about the bill's impact on adoption law.
Redefining marriage would allow same-sex partners to adopt as a couple, which Mr McCoskrie said was a change that was being "snuck under the door".
Mr McCoskrie also voiced concerns that independent celebrants could be coerced into marrying same-sex couples.
The bill allows celebrants who are part of religious organisations to decline marrying same-sex couples, but does not extend that to independent celebrants.
Mr McCoskrie said it was highly ironic that the Greens and Labour were determined to have a referendum on asset sales but would not allow one on marriage.
An attempt by New Zealand First leader Winston Peters to delay the law change, until a referendum could be held at the 2014 general election, was voted down by a margin of 83 votes to 33.
Ms Wall last night said the bill's progress had sent an important message to the gay, lesbian and transgender community.
"You don't have to change. You can be who you are."
She said marriage equality was about fairness and choice for all New Zealanders.
"Tonight's progress means those unable to access the institution of marriage for no reason other than their sex, sexual orientation or gender identity are a step closer in their fight against discrimination.
"The depth of feeling expressed by those in and out of Parliament has been moving. Parliamentarians on both sides of the debate spoke with honesty and with passion this evening."
She stressed the importance of freedom of religion in making the law change, but also made a plea to churches to consider the rights of the gay and transgender community "with love, compassion and reason".
The bill is likely to return to Parliament for the committee stage at the end of the month, when MPs will pick through it clause by clause.
It could be passed as soon as next month.
- Additional reporting by Isaac Davison of the NZ Herald