In 2012, Olmert, Jerusalem mayor and a Cabinet minister at that time, was acquitted of several corruption-related charges, including accepting large amounts of cash from US businessman Morris Talansky.
On Monday, the panel of judges found that Olmert accepted money from the entrepreneur as a personal bribe without reporting this fact during court hearings, according to local media reports.
The basis for the retrial in Talansky case was the testimony of Shula Zaken, a former aide of the ex-prime minister.
In May 2014, Olmert was sentenced to six years in prison for receiving bribes in exchange for assistance in the construction of the Holyland residential complex in Jerusalem. He pled innocent in the Holyland affair and is now appealing the verdict in the Supreme Court.
As of March 2015, Olmert is out of prison pending an appeal.
Olmert, 69, served as prime minister from 2006 to 2008. While in office Olmert stepped down to address charges brought against him.