A military jury in Hawaii found Army Specialist Christopher Shore not guilty of third-degree murder, but guilty of the lesser charge.
Shore had blamed his platoon leader – charged with premeditated murder – for the 23 June killing.
Shore could face up to eight years in jail, a dishonourable discharge and a drop to the army’s lowest pay grade.
During the trial, he said he had been ordered to fire at the Iraqi by his platoon leader, Sgt Trey Corrales.
The Iraqi was suspected of firing at a US helicopter. Shore denied killing the man, saying he had intentionally missed him.
Sentencing will take place later on Wednesday.
Sgt Corrales will stand trial on 22 April.