"We are pleased that you have taken this important step this afternoon.
"We're also pleased that you have decided to make Masterton and the Wairarapa your home."
The candidates, who were Dutch, Samoan, Chinese and British, were then invited to take the oath of allegiance or read their affirmation, after which they were presented with their citizenship certificates.
Tausulu Esera, from Samoa, said she and her family had moved from Samoa to Masterton in 2011.
"To get jobs and a better future for my family, and learn more skills and knowledge," Mrs Esera said.
She said they liked Masterton because it was "a peaceful place, not busy".
Another new citizen, Remco Jan de Ket, from Holland, has lived in New Zealand for the last 35 years and has spent almost eight years in Masterton.
Mr de Ket works as a nurse at Wairarapa District Health Board.
"Since I came here I've always felt that this is where I belong," he said.
After the ceremony, the families were invited to an afternoon tea and were presented with a kowhai tree to plant.