The Moscow city court sentenced ex KGB general Oleg Kalugin to 15-year imprisonment in a penitentiary in his absence.
The court found Kalugin guilty of high treason, pointing out that the ex general "encroached on the country's constitutional basis and security".
The court deprived Kalugin of his major-general rank and of all state awards he had received for his almost 40-year service in the USSR KGB.
The verdict can be appealed against during 7 days after it has been announced.
The companies involved in the implementation of the Nord Stream-2 project may deal with restrictive measures against them, a spokesman for the US Department of State said