A jury of US Army officers has convicted Major Nidal Hasan of all 13 charges of premeditated murder and all 32 charges of attempted premeditated murder for the November 2009 shooting spree at Fort Hood, Texas.
The convictions mean Hasan could face the death penalty by lethal injection.
The jury will begin hearing the penalty phase of the court-martial on Monday.
The US military has not executed a service member since 1961.
Hasan, a US-born Muslim and acting as his own defence lawyer, admitted in his opening statement to killing 13 people and wounding 31, saying he switched sides in what he considered a US war on Islam.
He was also charged with attempted premeditated murder on a 32nd person he shot at and missed.
Beyond the opening admission, the jury rarely heard from Hasan, who declined to make a closing argument on Thursday and rested his case on Wednesday without calling witnesses and without testifying in his own defence.
In their closing statement, prosecutors stressed that Hasan's rampage on 5 November 2009 was premeditated.
For Hasan to be eligible for the death penalty, the jury needed to find he killed at least two people, and at least one of those had to be a unanimous premeditated murder conviction.
The same jury of 13 officers will hear testimony in the upcoming penalty phase of the trial, making a recommendation for the judge, Colonel Tara Osborn, who will determine the sentence.
Hasan opened fire at an area where soldiers were being evaluated before being sent to Iraq or Afghanistan.