Military prosecutors had painted Fontana as a rogue and arrogant nurse who pumped patients full of fentanyl and morphine when they were not "dying quick enough." After the ruling, Fontana said he never second-guessed his treatment or dosages.
"My intention the whole time was to take care of dying patients," Fontana said.
Fontana, 36, said he wants to return to nursing.
Seeing the verdict as a validation, Fontana said he hoped the ruling would serve as a lesson for others tasked with making sure the terminally sick are comfortable. One doctor testified in the court martial that he worried the case would chill the use of painkillers on the gravely ill.
Elizabeth Higginbotham, Fontana's attorney, said during closing arguments that a guilty verdict would open the "floodgates" for lawsuits against nurses when a dying patient finally goes.
Col. William Burd, the military judge, also acquitted Fontana on one count of conduct unbecoming an officer for altering medical records.
"We have great confidence in our military justice system and we believe a fair verdict was reached today," the 59th Medical Wing said in a statement.
The hospital said Fontana will now undergo a clinical competency evaluation to determine whether he can return to being an Air Force nurse at the Wilford Hall Medical Center. He continued working at Wilford Hall while awaiting trial, though was stationed in the library.
During the weeklong trial, Air Force prosecutors accused Fontana of changing hospital records, trying to cover-up his tracks and chastising other nurses for not being aggressive enough in treating the end-of-life patients. They argued that Fontana knew the lethal effect of the dosages he was giving.
Fontana has been in the Air Force since 2006 and served a tour in Iraq in 2007. He worked as an intensive care nurse at Wilford Hall, which primarily serves military personnel and retirees but provides emergency and trauma care to some civilians.