Polk County Sheriff Johnny Moats said the Georgia prisoners, who all have committed minor crimes, would each have their sentences shortened by 25%.
The work crew had been cutting grass at a public cemetery when the corrections officer who was guarding them collapsed in the heat.
The six men used the guard's phone to call police and began performing CPR.
"When that happened, in my opinion, it wasn't about who is in jail and who wasn't," inmate Greg Williams told 11alive.com.
"It was about a man going down and we had to help him," he continued.
The work crew ran to the lone officer after he fell to the ground and removed his bullet-proof vest to perform CPR.
Rather than take his pistol and run off, they used his mobile phone to call for an ambulance.
"None of my guys ran," the officer told WKYC. "None of them did anything they shouldn't have done."
The family of the officer, who does not wish to be identified, bought a lunch of pizza and cupcakes for his incarcerated rescuers the next day.
Sheriff Moats said that "anytime we have a trustee or inmate crew that goes beyond normal duties, we cut them some extra time off".
The inmates' reaction also "really speaks a lot about my officers too, how they treat these inmates", he added. "They treat them like people. Like family."
Their actions come in stark contrast to two other Georgia convicts who were arraigned on Wednesday on charges of murdering two prison guards while being transported between prisons.
Prosecutors say they intend to seek the death penalty for Donnie Rowe and Ricky Dubose, who were captured in Tennessee after a three-day manhunt.
Six US prisoners are being rewarded for saving a prison officer who had suffered a suspected heart attack.