Kowhai trees were given to each of the new citizens, who all live within Central Otago.
Simon and Joanne Betney, of Queensberry, Nick Langley and Terry Smith, of Alexandra, Anne Pickard, of Omakau, and John MacDonald, of Cromwell, celebrated their formal status as New Zealanders with family and friends.
Central Otago mayor Malcolm Macpherson and wife Susan Macpherson undertook the ceremony at the Central Otago District Council chambers.
The new citizens shared a brief history and their reasons for moving to New Zealand, before they individually swore oaths or affirmations of allegiance.
Mr and Mrs Betney said they chose to live in Central Otago because it was "wild and real" and they could "see for miles".
Mr Langley married a New Zealander and they decided to settle in Alexandra when their son was born, because of the "generally good family values", while Miss Smith grew up in Wales and "felt at home" in New Zealand, where she chose to settle after a hectic city lifestyle in London.
A British Canadian, Mrs Pickard also married a New Zealander and after living in Canada for years the couple recently decided to make New Zealand their permanent home.
Mr MacDonald arrived in New Zealand from Glasgow in 1966, married a Dunedin woman, and lived in the city for 36 years before moving to Cromwell three years ago.
Being a New Zealand citizen would make it easier to visit his children living in Australia, he said.
About 30 St Gerard's Primary School pupils from Alexandra attended the ceremony and led the national anthem following formalities.
