Cameron, famous for his Titanic and Avatar films, owns more than 1500ha of land in South Wairarapa and has lived with his family in Wairarapa since 2012.
His second Avatar film - Avatar: The Way of Water - was largely made in New Zealand, with filming taking place in Auckland and Wellington.
RNZ has approached his production company Lightstorm Entertainment for comment.
In a statement, Minister for Internal Affairs Brooke van Velden said she was aware of Cameron gaining citizenship.
"Like thousands of people from across the world who choose to make New Zealand their home each year, I congratulate Mr Cameron on becoming a Kiwi.
"I think New Zealand is the best little country in the world, and I'm always happy to hear others think so too and wish to build their lives here."
