The soldier was the first member of the 1st Infantry Division, which is replacing the 4th Infantry Division, to die in Iraq, said Maj. Debra Stewart.
The soldier was killed after the Humvee he was riding in was hit by the bomb in Balad Ruz, just east of Baqouba in the Sunni Triangle. A second soldier was wounded in the explosion and airlifted the 31st Combat Support Hospital in Baghdad and was listed in stable condition.
The names of both soldiers were withheld pending notification of their families.
"It is a very sad day for the division, we have lost a very valuable team member," said Stewart, a Division spokeswoman.
The latest death brings to 553 the number of American service members who have died since the Iraq conflict began March 20. Most of those deaths occurred after President Bush declared an end to major combat May 1.