Exports exceeded imports by $534 million last month, pushing the annual trade surplus to $1.2 billion, its largest since July 2011.
But economists expect the improving trend in the annual trade balance to reverse when the sustained decline in dairy prices in Fonterra's fortnightly auctions over the past three months is reflected in the value of shipments crossing the wharves.
April is usually a surplus month and the latest surplus, equal to 12 per cent of exports, was in line with the average 13 per cent of exports over the previous five April months.
Exports at $4.5 billion were up $553 million or 14 per cent on April last year, despite a 2.8 per cent rise in the exchange rate over the year.
The lion's share (58 per cent) of the increase was in dairy products, but exports of forest products, fruit and crude oil were also well up on April last year.