Their crime? Defacing a Colorado nuclear missile silo in protest at the use of weapons of war.
Jackie Hudson will serve two and a half years behind bars while Ardeth Platte three and a half years and Carol Gilbert, a sentence of two years and nine months.
All three were also handed down sentences of three years' supervised probation.
"We're satisfied" with the outcome of the trial, prosecutor Robert Brown told CNN.
Cut and thrust
Hudson, 68, Gilbert, 55, and Platte, 66, were found guilty in April of “obstructing the nation's defence and damaging government property.”
They slashed open a fence to get to a Minuteman III silo, swung hammers at the structure and daubed a cross with their blood on the silo.
US District Judge Robert Blackburn was more lenient than required had he acted in accordance with sentencing guidelines.
He could have sentenced them all to maximum terms of 30 years. The minimum recommended sentence for such acts is six years in prison.
"These ladies could not be deterred for the last 20 years. They will be deterred for the time the court sentences them," Brown said. All three women have been arrested at peace protests in the past.
The nuns showed little emotion during the hearing, apart from turning to smile at supporters. They said they were not afraid of going to prison for their actions.
"The hope of the world rests on each of our shoulders," Hudson told reporters outside the court house. "We are doing our part. What about you?"