The industrial dispute at the Ports of Auckland may have affected trade figures.
Official figures show a trade surplus of $161 million in February, compared with a small deficit in January.
Exports fell nearly 7%, while imports declined 6.5%.
Statistics New Zealand says anecdotal evidence suggests the strikes at the Ports of Auckland may have delayed the loading and unloading of some goods.
The government agency says the impact of industrial disputes will become clearer when data for the March month and quarter are fully available.