Those arrested were embassy staff, the report by the official news agency IRNA said, adding that the U.S. forces confiscated computers and documents from inside the consulate building.
Tehran filed an official compliant with the Iraqi Foreign Ministry over the action.
Washington and Iraqi officials routinely blame Tehran for aiding Shiite militias responsible for dozens of assassinations in Iraq on a daily basis.
In December, U.S. forces arrested at least five Iranian agents in Baghdad, later handing them over to Iraqi authorities.
