Four were killed in a roadside bombing and a fifth was killed elsewhere.
Details are being withheld pending notification of next of kin.
Yesterday was the first day since October 10 that five US service members were killed in one day in Iraq.
US military deaths in Iraq have fallen on a month-to-month basis for four straight months.
Task Force Iron's operating area is the size of the US state of Georgia, stretching from Baghdad's northern suburbs to the borders of Turkey, Syria, and Iran in the north, west, ad east.
Task Force Iron is headquartered at Camp Speicher just outside Tikrit.