Pressure is rising on Lang to resign as president of the Arab World Institute in Paris since files released on January 30 by the US Department of Justice showed Epstein and Lang corresponding intermittently between 2012 and 2019, when the financier died by suicide in jail.
French media including Le Monde, Le Figaro and Mediapart said the preliminary investigation had been opened after the US documents revealed years of correspondence and financial links between Lang and Epstein.
The office confirmed the investigation but did not provide further details.
Jack Lang has been summoned to report on Sunday to the Foreign Ministry, which supervises the Arab World Institute, a cultural and research institution that promotes understanding of the Arab world.
Lang said on X that he welcomed the investigation "with serenity and even relief".
"It will allow all the light to be shed on accusations attacking my integrity and my honour," he added.
"The accusations levelled against me are baseless, and I will demonstrate this, beyond the sound and fury of the media and digital courts."
Lang's name appears more than 600 times in the Epstein files, according to a Reuters review of them. On Monday, Caroline Lang, a long-time media executive, resigned as head of France's Independent Production Union after her own links to Epstein surfaced.
Jack Lang's lawyer told BFM TV that he would "prove that he is not involved in any malpractice or criminal offence".
"There has been no movement of funds ... But I think it is normal for the justice to want to verify this," Laurent Merlet said.
The file dump has heightened scrutiny of Epstein's global connections with public figures including Britain's Andrew Mountbatten-Windsor - the younger brother of King Charles - Peter Mandelson, the former UK ambassador to the United States and Norwegian Crown Princess Mette-Marit.
