The victims were blindfolded, shot and dumped in a canal in April 2007.
Sgt John Hatley, Sgt 1st Class Joseph Mayo, and Sgt Michael Leahy Jr have been charged with premeditated murder, conspiracy to commit premeditated murder and obstruction of justice.
It was alleged that the killings were in retribution for casualties sustained by the soldiers' unit.
A pre-trial hearing will determine whether a court martial will be held, a spokesman for the Joint Multinational Training Command in Grafenwoeher, Germany, said.
Four other soldiers were charged with conspiracy over the same incident last week, AP reported.