Schreiber was found guilty in Augsburg state court, the German news agency DPA reported Thursday.
Prosecutors said he didn't declare money he received as kickbacks for the sale of helicopters to Canada's coast guard, tanks to Saudi Arabia and other arms deals.
Allegations the 79-year-old gave a cash donation to the former treasurer of Kohl's party triggered a scandal that deepened with Kohl's 1999 admission he accepted off-the-book donations himself.
Schreiber, a Canadian-German dual national, was arrested in Canada in 1999 and extradited to Germany after a 10-year battle. In Germany, he was convicted in 2010 but won a retrial on appeal.
In Canada, Schreiber was the key witness in a public inquiry into his business dealings with former prime minister Brian Mulroney. Justice Jeffrey Oliphant ruled the dealings were "inappropriate."
Mulroney admitted taking $225,000 in cash from Schreiber, but said he broke no laws or ethical guidelines.
Error in judgment
Mulroney argued that he had been hired by Schreiber merely to try to line up support from political leaders in Russia, China and France for a proposed United Nations purchase of armoured vehicles made by the Thyssen company in Germany. Schreiber was then a lobbyist for Thyssen.
Mulroney testified he made an error in judgment in accepting the money.
Schreiber said the payments totalled $300,000, not the $225,000 Mulroney later declared for tax purposes. He also maintained the former prime minister was supposed to lobby Canadian officials, not foreign leaders.
Schrieber was extradited after an Ontario court denied his bid to stay in Canada and after the public hearings into his controversial financial dealings with Mulroney had ended.