Chief Warrant Officer Lewis Welshofer Jr also was ordered on Monday to forfeit $6000 salary and was restricted to his place of work, worship and barracks for 60 days.
Welshofer, 43, had originally been charged with murder, but instead he was convicted on Saturday of negligent homicide and negligent dereliction of duty and faced up to three years and three months in prison, a dishonourable discharge, loss of his pension and other penalties.
The trial was held at Fort Carson in the US state of Colorado.
After hearing the sentence, Welshofer hugged his wife and soldiers in the gallery watching the trial; many who had worked with Welshofer and who testified as character witnesses, broke into applause.
The officer was accused of torturing Iraqi Major General Abid Hamad Mawhush, covering his head with a sleeping bag, binding him with an electric cord and sitting on his chest until he died.
The general died of suffocation at a detention centre in al-Anbar province, near the Syrian border in November 2002.
US military officials could not immediately be reached to confirm the sentence.