The ruling marks al-Majid's third death sentence for alleged crimes under Saddam Hussein's rule.
Al-Majid, a cousin of Saddam, was nicknamed "Chemical Ali" for overseeing the gassing of Iraqi Kurds during the so-called "Operation Anfal" campaign in 1988.
About 182,000 Kurds were estimated to have been killed in gas and bomb attacks during the operation and 4,000 villages destroyed.
Al-Majid was also accused of masterminding the gassing of 5,000 Kurds in the town of Halabja in a separate attack.
His executions have been delayed by legal battles.
Of 14 other defendants who were convicted of involvement in the attacks, the court sentenced two other former Baath officials to death and handed life imprisonment sentences to four others.
The court acquitted Tariq Aziz, Iraq's former deputy prime minister, on the same charges of crimes against humanity.
Aziz faces another trial for his alleged involvement in the 1992 execution of 42 Baghdad merchants who were accused of speculating on food prices.
Aziz, a Christian, surrendered to US forces in April 2003 after Saddam's regime was overthrown.
Saddam was hanged in December 2006 for the killing of 148 Shiite residents of Dujail following an abortive 1982 assassination attempt against the then-president in the mainly Shia town, north of Baghdad.
The US set up the Iraqi High Tribunal in 2004 to try former officials of Saddam's regime.