The Bucharest court on Thursday ruled Petcu is to spend seven years in prison and will be deprived of certain civil rights for a ten-year period.
The former union leader was also ordered to pay back nearly 1.4 million lei (EUR321,000) to the businessman who reported him for bribe-taking.
The court ruling may be appealed.
Petcu was placed under preventive arrest on March 31, after he was caught taking a EUR40,000 bribe from a businessman, but was released from custody on June 20, following a ruling of the Bucharest Court of Appeals.