One in five civil unions registered last year were between visitors to New Zealand.
Statistics New Zealand figures show 303 civil unions registered to New Zealand residents and 87 to overseas residents.
A statistical analyst, Anne Howard, says 88% of all civil unions were between same-sex couples.
She says while the figures don't show where the visiting couples come from, previous studies suggest most are from Australia and Britain.
"About two-fifths of couples coming here to either marry or form a civil union were from Australia and about one-quarter were from the United Kingdom.
"Couples coming here tended to have a strong connection to New Zealand."
Ms Howard says between 2005, when civil unions became legal, and the end of last year, 2455 residents registered for the ceremony and 124 civil unions were subsequently dissolved.
She says there were about 2500 marriages involving New Zealand residents last year, slightly less than the yearly average over the past decade.
Ms Howard says only one in 10 overseas visitors came here to get married.
The statistics also reveal that opposite-sex couples make up almost a quarter of civil unions.
They also show that people are getting married later in life, with the median age for first marriages for women at 28 and men at 30, compared with 25 and 27 years, respectively, in 1992.