In a case that saw appeals by the UN and Reporters Without Borders (RSF), Amadou Vamoulke, a former managing director of Cameroon Radio-Television (CRTV), was found guilty of illegally giving himself holiday pay worth $25,000 in 2005 and 2006.
He was also convicted of giving unauthorized bonuses to finance ministry personnel who had been seconded to the station.
The case was handled by a special criminal court designed to tackle major corruption cases.
Vamoulke, who became head of the CRTV in 2005, was arrested and detained in July 2016 and charged with defrauding public funds.
His trial suffered 137 postponements during his six and a half years in preventive custody.
"The entire case should have been cancelled," his lawyer Alice Nkom said.
"Amadou Vamoulke was denied freedom even before he was sentenced. There are millions of violations of human rights in this trial... the whole world has seen that he was arbitrarily detained," she told AFP, adding that he would appeal.
The 12-year sentence will take into account the time spent in custody.
In 2020, the United Nations' Working Group on Arbitrary Detention called for Vamoulke's release, saying that in addition to ill health, he had suffered violations to the right of a fair trial.
His case was also taken up by the media watchdog RSF, which last year said the accusations against him were based on "no serious evidence" and he was a victim of a "judicial plot."
The central African state has been ruled for 40 years by Paul Biya, 89.
RSF's 2022 Press Freedom Index ranks Cameroon 118th out of 180 countries.