Paraguay makes it three in a row while Latin American countries dominate happy index.
New Zealand is among the 20 happiest countries in the world.
Gallup's latest positive experiences index has ranked New Zealand 15th equal with Canada, Australia and United Arab Emirates.
Paraguay was found to be the happiest country out of 138 - for the third year in a row - while Syria, which is going through a civil war, was the unhappiest, scoring an all-time low for any country Gallup has measured.
Gallup surveyed 1000 adults in each of the countries asking five questions: if they felt rested, felt they were treated with respect, laughed or smiled a lot, whether they experienced enjoyment and whether they had done something interesting the day before.
"What we wanted to find out was what was driving those five things," said Jon Clifton, managing director of Gallup World Poll.
He said workplace or school for students, sense of community and financial wellbeing were big contributing factors.
Business psychologist Jasbindar Singh said Kiwis were generally happy because we have a good standard of living with access to jobs and resources.
"We live in a country where people have a sense of choice and say in the matter, and we are not mired in political unrest or instability," she said.
"I think most Kiwis have access to a positive lifestyle, are pretty laid back, enjoy their weekends ... all these generate positive emotions and a positive story which in turn contribute to feelings of happiness."
Most of the happiest countries are in Latin America, with the other countries in the top five being Panama, Guatemala, Nicaragua and Ecuador.
Chad, Lithuania, Serbia, Nepal and Belarus all featured among the least happy countries.
On average, 70 per cent of adults worldwide said they were experiencing lots of enjoyment, laughing or smiling a lot, feeling well rested and were being treated with respect.
The survey also found that people who make more money tended to report higher positive emotions - but only up to around US$75,000 ($88,000).
3= Guatemala, Nicaragua, Ecuador
6= Costa Rica, Colombia, Denmark
9= Honduras, Venezuela, El Salvador
12= Indonesia, Philippines, Thailand
15= New Zealand, United Arab Emirates, Canada, Australia
Source: Gallup Positive Experience Index.