“News of the individual’s arrest is correct”, Gholam Hossein Mohseni Ejei said, speaking at a weekly press conference in Tehran.
He added, however, that the person was released on bail after a few days.
The official did not give any details about the individual or charges against him.
His remarks came after an Iranian lawmaker last week said a person close to the nuclear negotiating team had been arrested on charges of espionage.
Iran’s nuclear negotiators and representatives of the Group 5+1 (Russia, China, the US, Britain, France and Germany) held several rounds of talks over a period of 22 months before they reached an agreement on Tehran’s peaceful nuclear program in July 2015.