The military jury handed down the sentence a day after convicting Sergeant Michael J Smith, 24. He could have gotten eight and a half years in prison.
Smith was sentenced on five charges, including maltreatment of prisoners, conspiring with another dog handler in a contest to try to frighten detainees into soiling themselves, and directing his dog to lick peanut butter off other soldiers' bodies.
Prosecutors said he let his unmuzzled black Belgian shepherd bark and lunge at cowering Iraqis for his own amusement. The defence argued that Smith believed he was following orders to soften up prisoners for interrogation.
Smith appeared unrepentant when he addressed the jury on Tuesday, shortly after he was convicted.
"Soldiers are not supposed to be soft and cuddly," he said.