Michael Waipouri has been found guilty of murdering and kidnapping his long-time friend, Lance Murphy.
Mr Murphy's body was found at a rural property in Wellsford in 2015. He had been beaten to death with a baseball bat and a tree branch on the remote hilltop north of Auckland.
Another man, Steve Gunbie, was charged with kidnapping and being an accessory, but was found not guilty.
Jury members took two hours to make their unanimous decision.
Waipouri, who is also known as Michael Davies, will be sentenced in the High Court in Auckland in April.
During the trial, Waipouri's lawyers said he had a paranoid condition but acted in self defence when he killed Mr Murphy, a man he had known for three decades.