The BBC reported that former British SAS officer Simon Mann has been convicted by a Zimbabwe court of illegally trying to buy weapons.
The men were arrested in March when they landed at Harare Airport. They denied plotting a coup.
The other alleged mercenaries and the plane's pilots were sentenced to either 12 or 16 months in prison.
The men always said the weapons were to be used to provide security for mines in the Democratic Republic of Congo.
"The accused [Simon Mann] was the author of the whole transaction.