David Owen Lyttle has been found guilty of murder by a unanimous High Court jury in Wellington.
Lyttle was on trial in the High Court in Wellington for the murder of his friend Brett Hall in May 2011.
Mr Hall, who was 47, went missing from his Whanganui property in May 2011 and his body has never been found.
Lyttle, 54, was targeted three years later by a police operation called "Mr Big", in which undercover officers posing as gangsters promised him money and opportunities if he told them the truth about his friend's disappearance.
The Crown said Lyttle admitted to undercover police in 2014 that he had killed him.
The defence team claimed the confession was just a story.