Abdullah Yasser Sabawi, the grandson of Saddam's half-brother Sabawi Ibrahim Al Tikriti, was detained in the Lebanese city of Jbeil in August and was extradited on November 9, a security official told AFP on condition of anonymity.
"He is accused of having been a member of ISIS and having participated in the Speicher massacre", in which as many as 1,700 air force cadets were executed by the terrorist group, said the security official.
Mr Sabawi has reportedly lived in Lebanon for years.
The massacre at Camp Speicher, near Saddam's home town of Tikrit, became a symbol of ISIS brutality as the terrorist group expanded its presence in Iraq.
Mr Sabawi, born in 1994, was detained after an Interpol notice called for his arrest over his alleged involvement in the killing, according to a Lebanese judicial source.
"Iraq requested his extradition," the source said.
Mr Sabawi's family has denied the accusations, telling AFP he was in Yemen at the time of the massacre.
The fall of Tikrit in 2014 was part of the ISIS onslaught that stunned Iraqi security forces and the military, which melted away as the militants advanced and captured key cities and towns in the country’s north and west.
Nearly 3,000 cadets from all over Iraq were ordered by their superiors to change into civilian clothes and leave Camp Speicher after the fall of Mosul in June 2014.
Those carrying weapons were told to leave them behind.
Many of the cadets were captured by the insurgents, who took them to various locations around Tikrit and executed them one by one in the worst single atrocity committed by the group.
Videos showed masked gunmen bringing the victims to a bloodstained concrete river waterfront inside the presidential palace complex in Tikrit, shooting them in the head and dumping them in the Tigris.