Great Mercury Island -- part-owned by one of New Zealand's richest men, Sir Michael Fay -- has been declared pest-free.
The island, which lies off the coast of the Coromandel Peninsula, has been under surveillance for the last two years following a comprehensive pest eradication programme.
With no rodents found, the island has been formally declared pest-free by Conservation Minister Maggie Barry.
"Since 2014 Great Mercury has already seen the return of kakariki and seabirds which had been driven off it by pests -- a sure sign the eradication has worked," Ms Barry said.
The entire Mercury island group, along with the nearby Ohinau group and the Alderman Islands are now free of pests like rats and feral cats.
The pest eradication programme on Great Mercury Island was a partnership between the Department of Conservation and Sir Michael.