The survey records the number of stays in hotels, motels, backpacker accommodation and holiday parks in New Zealand each month. Each guest night is equivalent to one guest spending one night at an establishment.
Northland Inc regional promotions and tourism manager Paul Davis said the year end increase was "really, really healthy".
"There's been strong growth across all international markets," he said. "We're also starting to see an emergence of visitors from relatively new markets for us such as China, South America and India."
Domestic visitor numbers were also positive, he said.
"The other story over the past year has been the strong growth in domestic accommodation nights. We've been seeing more commercial travel to Whangarei and a pick up in the leisure sector in the Far North and Kaipara."
The Fifa U-20 World Cup had brought good numbers to the region, he said.
"Events always interest people. They're great because they create focus on Northland and give people a reason to travel here."
Nationally, guest nights were up 5.5 per cent year-on-year. As in the previous three months, most of the rise for May was from international guest nights, which were up by 11 per cent. Domestic guest nights were up 5.2 per cent.
Motel Association of NZ chief executive Michael Baines said the figures reflected a strong year for tourism so far.
"We've had an awful lot of Aussies coming, and the economic recovery in Europe has brought back the English market that disappeared for a while," he said.
"There's also good and strong continual growth out of the United States and year-on-year growth from China."
Domestic tourism was also positive, he said.
"No one should underestimate the power of domestic tourists. Lower fuel prices, job retention and a more positive view on the economy are giving people the confidence and ability to explore."
The recent batch of bad weather around the country had not been too disruptive, he said.
