Former Green Party co-leader Russel Norman has pleaded guilty to trying to obstruct the largest oil exploration ship in the world last year.
Mr Norman - Greenpeace's executive director - and climate activist Sara Howell swam in front of the Amazon Warrior in April last year, forcing it to stop its search for oil for the day.
A week-long trial was due to start today at the Napier District Court, but the Ministry for Business, Innovation and Employment last week indicated that it would drop charges against Greenpeace if the pair pleaded guilty themselves.
Greenpeace had faced fines of up to $200,000 under the 2013 controversial "Anadarko Amendement" in the Crown Minerals Act, which made it an offence to interfere with oil exploration ships at sea.
It was the first time anyone has been charged with the crime.
Appearing via video link from Auckland, Mr Norman and Ms Howell pleaded guilty and were remanded on bail, on the condition that they must not offend again against the Crown Minerals Act.
Judge Geoff Rae questioned whether that was necessary but the lawyer acting for MBIE, Cameron Stuart, argued it was given there were current protests over offshore oil exploration in Taranaki.
Both Mr Norman and Ms Howell have sought discharge without conviction and will appear again in Napier District Court for sentencing on 6 July.