The court sentenced Ali Hassan al-Majid, a cousin of former Iraqi President Saddam Hussein, to be hanged for ordering chemical-gas strikes, crimes against humanity, war crimes, and genocide.
Al-Majid reportedly declared "Thanks be to God" after hearing the verdict.
RFE/RL's Iraq Service reports a current curfew in Baghdad may mean a muted public response to the verdict.
'Spoils Of War'
The case relates to the series of military operations code-named Anfal (Spoils of War) that were conducted against ethnic Kurds in 1988, which prosecutors say killed up to 180,000 people.
Sultan Hashim Ahmad, the commander of the Anfal campaign who reported directly to al-Majid, was also sentenced to death for his role ordering a large-scale attack against civilians and using chemical weapons and deportation against the Kurds.
Husayn Rashid al-Tikriti, former army chief of staff and secretary-general of the General Command of the Armed Forces, likewise received a death sentence after being convicted of drawing up military plans aimed at attacking the Kurdish population.
Al-Tikriti reportedly interrupted the judge as his verdict was being delivered, saying, "Thank God, because we defended Iraq and we were not criminals."
Five Of Six Sentenced
Two additional defendants, Farhan al-Juburi and Sabir al-Duri, received life sentences.
Charges were dropped, however, against a former governor of the main northern city of Mosul, Taher al-Ani, for lack of evidence.
The Amman-based defense team said it planned to appeal the sentences.
Human Rights Watch has said the Anfal trial has been marred by procedural flaws.
President Hussein, driven from power by the U.S.-led invasion in April 2003, was executed last December for crimes against humanity in a separate case.