The Appeals Chamber affirmed the Trial Chamber's decision to convict Stakic, 44, for his responsibility in exterminating, murdering and persecuting the non-Serb population in Prijedor in 1992.
About 3,000 Muslims and Croats were killed during an ethnic cleansing campaign in Prijedor, particularly in Serb-run concentration camps Omarska, Keraterm and Trnopolje.
Citing the names of 486 victims, the Trial Chamber said Stakic was responsible for 1,500 murders and sentenced him to life imprisonment, the maximum penalty and the tribunal's first life sentence.
The Appeals Chamber found that the Trial Chamber incorrectly failed to convict Stakic for deportation and forcible removal of the non-Serb population. It also found that the Trial Chamber committed some errors in determining his sentence, but noted that the impact of the errors on the sentence was limited.
The Appeals Chamber agreed with the Trial Chamber's decision to acquit Stakic of genocide and complicity in genocide.
The time Stakic has spent in detention since 23 March 2001 will be credited towards his prison sentence.