It was the latest legal blow in a humiliating fall from grace for the debonair man who took over as prime minister in 2006 after his mentor and predecessor Ariel Sharon lapsed into a coma from which he never recovered.
"We find the defendant guilty of fraud and a breach of trust," the Jerusalem district court verdict read, "and of the felony of fraud under aggravated circumstances."
Sentencing for the 69-year-old, who already faces a six-year prison sentence in a separate bribery case that he has appealed to the supreme court, is scheduled to begin on May 5, the verdict stated.
He had initially been acquitted of fraud and corruption in the case, escaping in 2012 with a USD 19,000 fine and a suspended jail sentence for breach of trust.
Also Read
But new evidence came to light during his trial in the other corruption case, and prosecutors again pressed the charges.
In return for a reduction in sentence, his former secretary and confidante Shula Zaken brought to the court secret recordings of conversations she had with Olmert.
The six-year prison sentence handed down against Olmert in May last year was the first ever against a former Israeli premier for corruption.
After a two-year trial, he was convicted of taking bribes to the tune of 560,000 shekels (now USD 140,000/129,000 euros) while mayor of Jerusalem between 1993 and 2003 from the developers of the city's massive Holyland residential complex.
The towering construction project, which dominates the city's skyline, is seen as a major blot on the landscape and widely reviled as a symbol of high-level corruption.
Before taking over as premier in 2006, Olmert was recognised as a key strategist behind many of Sharon's boldest moves, including Israel's 2005 withdrawal from the Gaza Strip and his decision to leave the rightwing Likud and form the centrist Kadima party.
After Sharon's collapse, Olmert led Kadima to victory in March 2006 on a platform of dismantling dozens of settlements and withdrawing troops from most of the West Bank.