Oil explorer OMV says oil is being produced from the new Maari oil field off the Taranaki coast.
The OMV operation is the largest in New Zealand and is expected to produce some 50 million barrels over its predicted lifetime of 10 years to 15 years.
Two of the oil field's eight wells have been completed and one is now in use.
The company expects the rest of the wells should be fully functioning by the end of this year.
OMV says the offshore Taranaki field production testing will take place over the next couple of week to make sure the oil is ready to be processed.