Ble Goude headed the notorious Young Patriots street militia during Gbagbo's presidency.
Gbagbo and Ble Goude were acquitted in January by the International Criminal Court (ICC) in The Hague of charges of crimes against humanity during the violence, in which some 3,000 people were killed.
But Ivorian prosecutors this month brought charges against Ble Goude - who has remained in Europe while ICC prosecutors appeal against the acquittals - for rape, torture and other crimes related to his role in the conflict. He denied the charges.
Political tensions are rising in Ivory Coast ahead of an October 2020 presidential election. President Alassane Ouattara, whose victory over Gbagbo in 2010 sparked the civil war, is expected to step down after 10 years in office, but he has refused to rule out running for re-election.
Ble Goude's lawyer in the Netherlands, Geert-Jan Knoops, said on Tuesday the Ivorian court had convicted his client on Monday.
"I am quite astonished that a country that is supposed to cooperate with the ICC is not respecting the system," Knoops said. "Once a case is before the ICC, the domestic courts should abstain from prosecution for the same facts."
Ble Goude's lawyer in Ivory Coast, Ndry Claver, said a warrant had been issued for Ble Goude's arrest.
An official at the court in Abidjan confirmed the sentence. A government spokesman was not immediately available for comment.
Ivory Coast extradited Ble Goude to the ICC in 2014.
Gbabgo also remains in Europe pending the ICC appeal. If he is able to return to Ivory Coast in time, he could stand in the presidential election, a move that Ouattara said would make him rethink plans to step down.