Momcilo Krajisnik was a former assistant to Radovan Karadzic, the Bosnian Serb wartime leader.
He was found guilty of murder, extermination, deportation, persecution and forced transfer of non-Serb civilians.
Judge Alphons Orie said: "Mr Krajisnik wanted the Muslim and Croat populations moved out of Bosnian-Serb territories in large numbers, and accepted that a heavy price of suffering, death and destruction was necessary to achieve Serb domination."
Orie cleared Krajisnik of genocide, saying he did not have the specific intent necessary to be found guilty of such a charge.
The verdict was dismissed as far too lenient by outraged relatives of some of the 8,000 Muslims killed during the massacre in 1995.
Sabaheta Fejzic, whose husband and only son were both killed, said: "Genocide was committed in Srebrenica and The Hague court confirmed that. All those indicted for genocide should be sentenced for it."
Munira Subasic, the president of the Sarajevo-based association of Srebrenica mothers, described the sentence as "Yet another reward for the crime committed against us in Bosnia and Herzegovina, yet another disappointment."
"Yet another reward for the crime committed against us in Bosnia and Herzegovina, yet another disappointment"
association of Srebenica mothers
Krajisnik, 61, was captured by Nato-led peacekeepers in 2000. He went on trial in Febraury 2004 charged with genocide, complicity in genocide, crimes against humanity and violating the laws or customs of war.
Krajisnik had pleaded not guilty to all charges. He was among the most senior politicians on trial at The Hague's war crimes tribunal since Slobodan Milosevic, a former president of Yugoslavia, died before his own trial was concluded.
Krajisnik led the parliament of the breakaway Bosnian Serb republic during the war. He was part of the presidency together with Karadzic and Biljana Plavsic, the former Bosnian Serb president.
Plavsic, who admitted responsibility for atrocities in the Bosnia war and was jailed for 11 years in 2004, testified against Krajisnik earlier this year.
Karadzic, who is still on the run, is charged with responsibility for the 1995 Srebrenica massacre of up to 8,000 Muslims and the siege of Sarajevo.