Foreign Minister Jean-Noël Barrot said the two diplomats were stopped on Sunday evening, held without explanation and interrogated before being allowed to return to the French embassy.
"One of them was physically abused," Barrot said, describing the incident as an "extremely serious act of intimidation" and a "flagrant violation of diplomatic immunity." Both officials are now safe and are expected to return to France within hours, he added.
According to Barrot, the two officials oversaw French programs supporting Iranian civil society, particularly artists and scientists.
He said he had informed Iranian Foreign Minister Abbas Araghchi that the incident was "serious and unacceptable" and "cannot go without consequences."
The incident comes amid sharply deteriorating relations between Paris and Tehran.
Last week, Barrot reiterated that France would oppose lifting sanctions on Iran unless Tehran abandoned its nuclear ambitions and what Paris describes as its destabilizing regional activities.
France has also pushed for a broader European role in negotiations over Iran's nuclear program and regional policies.
The two countries have also been locked in a long-running dispute over French nationals held in Iran.
France continues to demand the release of Cécile Kohler and Jacques Paris, who have been imprisoned in Iran since 2022. Paris has described their detention as arbitrary and has accused Tehran of using foreign nationals as diplomatic leverage.
Earlier this year, France filed a case against Iran at the International Court of Justice over alleged violations of consular rights.
The detention of embassy staff marks a further escalation, extending tensions beyond disputes over detained citizens to diplomats protected under international law.
Iranian authorities had not publicly commented on the incident by Monday evening.
