Col. Greg Hapgood of the Iowa Army National Guard confirmed Tuesday that Giunta decided not to re-enlist.
His contract with the Army is up in June.
Giunta is the first living service member from the wars in Afghanistan or Iraq to receive the Medal of Honor, the nation's highest military honor.
He was serving as a rifle team leader in Afghanistan when his platoon was attacked in 2007.
In announcing the award, the White House noted he went beyond the call of duty by exposing himself to enemy fire to pull a soldier back to cover. He also shot two insurgents who were trying to carry away a U.S. soldier.