The Army psychiatrist has never denied being the gunman, saying the attack on unarmed soldiers was motivated by a desire to protect Muslim insurgents fighting in Iraq and Afghanistan.
The jury that sentenced him to death also found him guilty last week in the attack.
The federal government has sought to execute Hasan for nearly four years, believing that any other sentence would deny justice to the families of the dead and the survivors who had believed they were safe behind the gates of the Texas base.
Hasan has seemed content to go to the death chamber for his beliefs. He fired his own attorneys to represent himself, barely put up a defense during a three-week trial and made almost no effort to save his life.
The troops were standing in long lines to receive immunizations and doctors' clearance when Hasan began shooting. Thirteen people were killed and more than were 30 wounded. All but one of the dead were soldiers, including a pregnant private who curled on the floor and pleaded for her baby's life.
The attack ended only when Hasan was shot in the back by an officer responding to the shooting. Hasan is now paralyzed from the waist down and uses a wheelchair.
Hasan spent weeks planning the Nov. 5, 2009, attack, including buying the handgun and videotaping a sales clerk showing him how to change the magazine.
Death sentences are rare in the military, which has just five other prisoners on death row. The cases trigger a long appeals process, and the president must give final authorization before any service member is executed.
No American soldier has been executed since 1961.
The Associated Press contributed to this report.
