The biggest falls in milk powder, butter and cheese products exports were to China and the United Arab Emirates, while the biggest drop in meat exports was to the US and UK.
The decline in monthly imports was led by a 17 percent fall in capital goods such as transport equipment and machinery to $967m and a 38 per cent slump in crude oil to $175m. Imports of vehicles, parts and accessories rose 13 per cent to $767m last month from August 2015.
ASB Bank economist Jane Turner said the deficit was much larger than the market expected, though August is typically a weaker month for New Zealand's agricultural exports.
"The key driver of the surprise for us was weaker exports (in particularly dairy), but imports were significantly stronger than the market was expecting as well," Turner said in a note. "Over the coming year, we expect declines in dairy export volumes as NZ production falls."
On an annual basis, annual exports slipped 0.5 per cent to $47.8b and imports fell 1 percent to $51.93b to post a trade deficit of $3.13b. China was the country's biggest trading partner, accounting for about 19 per cent of two-way trade.
Despite taking less milk powder, butter and cheese, China bought more exports in August, up 2 percent to $634m, and was just one of three of New Zealand's biggest export destinations to increase their purchases from a year earlier.