According to Jordanian news outlet al-Ghad, the soldier who shot three United States military trainers last November in al-Jafer airbase in Ma'aan governorate has been sentenced to life imprisonment by a Jordanian military court.
One was killed at the base and two others died later in hospital.
The defendant, 1st Sgt. Marik al-Tuwayha, had pleaded "not guilty", saying he opened fire because he feared the base was coming under attack.
The parents of one of the slain USA soldiers and the father and sister of another sat quietly as the judge announced his ruling to a crowded courtroom.
Jordan is a close ally to the USA and is a member of the US -led anti-Daesh coalition.
Jordanian authorities initially claimed the U.S. nationals had been killed when their vehicle failed to stop.
In the attack, for which no extremist motive has been proven, he killed Staff Sgt. Matthew C. Lewellen, a 27-year-old from Missouri; Staff Sgt. Kevin J. McEnroe, a 30-year-old from Arizona; and Staff Sgt. James F. Moriarty, a 27-year-old from Texas.
The US soldiers' family members were in court to hear the verdict on Monday.
In Jordan, life in prison can mean 20 years, with time off for good behavior.
Jordan, a Middle East monarchy, is a key US ally, providing Washington with an area of operations that has relative stability and a strategic location that has allowed it to work toward its aims in the Syrian civil war and the fight against the Islamic State militant group (ISIS), carrying out bombing raids from Jordanian airfields.