Official statistics show there were 19,237 marriages registered to New Zealand residents last year, dropping below 20,000 for the first time since 2001.
This is despite same-sex couples being granted the right to get married for the first time last year.
There were a total of 355 same-sex marriages.
Overseas residents accounted for 41 per cent of the same-sex marriages in New Zealand last year, compared with just 11 per cent of opposite-sex marriages.
Of the same-sex marriages of non-New Zealand residents, 65 per cent were from Australia, where same-sex marriage is illegal. However, Australians also made up 58 per cent of the 2270 opposite-sex marriages of foreigners.
Same-sex civil unions almost halved compared to 2012, though opposite-sex civil unions were constant.
There were 8279 divorces in 2013, down from 8785 the previous year.
Statistics New Zealand estimates that for every 1000 existing marriages in New Zealand, there were 9.4 divorces.
It says 35 per cent of couples married in 1988 have since divorced.