The court in Mannheim, southwest Germany, found the 60-year-old guilty of acting as a middleman to send equipment to Iraq that could be used to produce gun barrels for nuclear, chemical or biological weapons.
In its ruling, the court said the man, whose name was not made public, had been a kind of "estate agent" for the weapons industry, adding: "It was not a mistake."
It said it believed the equipment was to have been used to manufacture NBC weapons.
The accused was arrested in Bulgaria at the end of 2002 and extradited to Germany in March.
Four accomplices were given fines or suspended sentences at a hearing in early October.