The helicopter went down about 8:30 p.m. near Qayyarah, some 30 miles south of Mosul, the military said.
The cause of the crash was unclear. The military said "an initial report from the accompanying second helicopter did not make mention of hostile activity."
Friday's deaths brought to 507 the number of American service members who have died since a U.S.-led coalition launched the Iraq war March 20. Most of the deaths have occurred since President Bush declared an end to active combat May 1.
It was the fourth helicopter crash suffered by U.S. forces in Iraq this month.
On Jan. 2, an Army OH-58 Kiowa Warrior helicopter was shot down near the central city of Fallujah, killing one pilot. Six days later, an Army Black Hawk medevac helicopter was shot down by a rocket near Fallujah, killing all nine U.S. soldiers aboard.
A U.S. Army Apache attack helicopter was brought down by apparent enemy fire on Jan. 13, but both crew members escaped injury.
On Nov. 15, two U.S. Army Black Hawk helicopters collided and crashed in Mosul, killing 17 American soldiers in the U.S. military's worst single loss of life since the Iraq war began.