Vows were exchanged in venues ranging from an airliner cruising at 30,000 feet (9,150 metres) to a historic bath house as gay men and women took advantage of the law change.
The Campaign For Marriage Equality said it ended an historical injustice and meant the love of all people was recognised as equal in the eyes of the law.
"A massive congratulations to the happy couples tying the knot today. Marriage equality has finally arrived in New Zealand," spokesman Conrad Reyners said.
The amendment to the Marriage Act was passed by parliament in April but did not come into effect until Monday.
Two radio stations competed to host the first same-sex wedding, with the ceremonies broadcast live during their breakfast programmes.
In reality, the nuptials took place around the same time, at 8.30 am Monday (2030 GMT Sunday), after the government offices that issue marriage licences had opened.
Reverend Matt Tittle from Auckland's Unitarian Church married one of the couples, Tash Vitali, 37, and Mel Ray, 29, who arrived at the ceremony in a horse-drawn carriage trailing a rainbow banner.
"It's history in the making," Tittle said.
"Hopefully it will help other countries to do the same and help New Zealanders to realise that everyone has worth and dignity no matter who they love."
Air New Zealand staged a special flight from Queenstown to Auckland where Lynley Bendall and Ally Wanikau tied the knot in the air after 14 years together, with American gay rights campaigner and actor Jesse Tyler Ferguson from the hit comedy "Modern Family" in attendance.
"To be married at 30,000 feet beneath strings of fairy lights with our children, friends and family as witnesses makes an already memorable day that much more special," Bendall said.
Wellington couple Jonathan Major and Marshall Donnelly opted for a simpler wedding attended by half a dozen friends and relatives at a city centre registry office .
"It hardly seems real," said Major before the ceremony began, as his teenage daughter Naeve joked: "It's not too late to back out."
However, conservative lobby group Family First said changing the Marriage Act was "an arrogant act of cultural vandalism" that politicians had pushed through without a public mandate.
"Social engineers including politicians and activists are expecting marriage supporters to drop their deeply held convictions because of the misguided decisions of politicians," said national director Bob McCoskrie.
The Anglican Church has also asked its ministers not to conduct same-sex weddings pending a report to its general synod next year.
New Zealand decriminalised homosexuality in 1986 and has allowed same-sex civil unions since 2005.
The Department of Internal Affairs said the number of marriage licence applications downloaded from its website had tripled in the week leading up to the law change.
At least 31 same-sex couples planned to marry Monday, while enquiries about staging same-sex weddings in New Zealand had been received from Russia, the United States, Hong Kong, Britain, Singapore, Malaysia, Guyana and Belgium.
Among the first to be married were Australian couple Paul McCarthy and Trent Kandler, who beat 300 other pairs to win a Tourism New Zealand competition.
Their wedding will not be legally recognised at home but McCarthy said he hoped that day would come and the ceremony at Wellington's Te Papa museum showed "we don't have two horns, we're not freaks (and) that there's nothing to fear from marriage equality".
About 1,000 same-sex couples in Australia have indicated they plan to travel to New Zealand to marry, according to the Australian Marriage Equality lobby group.
Tourism New Zealand chief executive Kevin Bowler said the country would market itself as a same-sex destination.
"New Zealanders are incredibly tolerant of people with different lifestyles, so I'm very confident the industry will embrace this opportunity," he told TV3.