The country gained 3,800 new migrants, seasonally-adjusted, in March, the most since February 2003, Statistics New Zealand said.
A net 400 people left for Australia in March, down from 600 in February, according to seasonally-adjusted figures.
In the year through March, New Zealand gained 31,900 migrants, a 10-year high, as 98,000 people arrived while 66,100 left.
That’s more than 12 times the 2,500 annual migration gain in the year through March 2013 and compares with an average gain of 11,700 migrants during the past 20 years.
In the latest year, New Zealand had a loss of 12,900 migrants to Australia, well down from 35,500 a year earlier.
Gains were recorded from most other countries, led by China 6,200, India 6,100, and the UK 5,800.
The Reserve Bank of New Zealand in March said the rapid increase in net migration in the past 18 months was an inflationary pressure which prompted it to lift the official cash rate (OCR) a quarter-point to 2.75 per cent.
The central bank is widely expected to hike the OCR a further 25 basis points when it reviews the rates on Thursday.