Nidal Hasan could be sentenced to death by lethal injection after being found guilty of 13 charges of premeditated murder and all 32 charges of attempted premeditated murder after he went on a shooting spree at the Fort Hood base in Texas in November 2009.
The last soldier to face execution at the hands of the US military was in 1961.
Hasan was paralysed from the waist down when shot by police to end the rampage in which he killed many unarmed soldiers.
He stared at the 13-officer jury while the panel's president read the verdict then looked down, stroking his beard.
Jurors will begin hearing the penalty phase of the court-martial on Monday and make a recommendation to the judge, Colonel Tara Osborn, on sentencing.
Hasan, 42, told mental health evaluators he wanted to become a martyr. Lawyers assisting Hasan said he was actively seeking the death penalty, though Hasan disputed that claim.
The American-born Muslim acted as his own defence lawyer. He admitted to causing the deaths and injuries 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. Nearly all of the dead and wounded were fellow soldiers.
In their closing statement, prosecutors stressed that Hasan's rampage on November 5 2009 was premeditated.
Prosecutors called 89 witnesses, with many describing in horrific detail the bloodbath in and around a medical building at Fort Hood. It was the worst non-combat attack ever at a US military base.