Spc. Brian Leonhardt, of Merrillville, has been promoted posthumously to sergeant.
Army regulation allows fallen soldiers in line for promotions to receive the honors.
Leonhardt was one of four guardsmen killed while clearing roadside bombs last week.
Pvt. Douglas Rachowicz, of Hammond, who was injured in the blast, was promoted to private first class.
He's in a medically induced coma at Walter Reed National Military Medical Center with several injuries.