The reports said Jalal Sharafi, the second secretary at the Iranian Embassy in Baghdad, is expected to return to Tehran later today.
The reports gave no indication of how or why Sharafi had been released.
He was seized in early February by armed men dressed in Iraqi Army uniforms.
Iran said he had been taken by an Iraqi commando unit that reports to the U.S. command.
U.S. officials have strongly denied the allegation.
Sharafi's abduction took place nearly a month after U.S. troops detained five Iranians in northern Iraq and accused them of having links to a network backing armed Shi'ite groups.