Moody's says New Zealand's economy and Government finances are improving following a recession and the Canterbury earthquakes.
In a statement, the ratings agency said economic growth is accelerating, in part because of earthquake reconstruction.
Moody's rates New Zealand as AAA, with a stable outlook, a notch above the other two agencies, Standard & Poor's and Fitch.
Moody's says the economy and the government's finances are improving following a long, but mild recession and the Canterbury earthquakes.
It says the economy is accelerating, partly because of the rebuild following those earthquakes, and it expects the economy will grow by three percent in 2014.
This expectation is underpinned by the Government's forecast of a small surplus next year.
However, the agency said New Zealand's continued reliance on foreign savings is a risk.
Deutsche Bankchief economist Darren Gibbs said the rating came as no surprise.