Judges found former president Nicolas Sarkozy guilty of trying to bribe a judge and of influence-peddling on Monday and sentenced him to three years in jail, with two years suspended.
Mr Sarkozy, who led France from 2007 to 2012, had denied any wrongdoing, saying he was the victim of a witch-hunt by financial prosecutors who used excessive means to snoop on his affairs.
Retired from politics but still influential among conservatives, Mr Sarkozy has 10 days to appeal the ruling.
He is the second former president in modern France, after the late Jacques Chirac, to be convicted of corruption.
Prosecutors persuaded the judges that Sarkozy had offered to secure a plum job in Monaco for judge Gilbert Azibert in return for confidential information about an inquiry into allegations that he had accepted illegal payments from L'Oreal heiress Liliane Bettencourt for his 2007 presidential campaign.
This came to light, they said, while they were wiretapping conversations between Sarkozy and his lawyer Thierry Herzog after Sarkozy left office, in relation to another investigation into alleged Libyan financing of the same campaign.