Lagarde has been accused of influencing the outcome of 2008 court process instigated by French entrepreneur Bernard Tapie against Credit Lyonnais bank. Lagarde, who served as the French finance minister at the time, referred the case to private arbitration, which resulted in a 400-million-euro ($450-million) payment to Tapie. This decision is alleged to have been aligned with the government agenda.
According to Le Parisien newspaper, the judges ruled that Lagarde was guilty, but did not hand down any sentence.
Lagarde's lawyer promised to appeal the ruling.
The decision might trigger an IMF crisis. Lagarde's predecessor Dominique Strauss-Kahn stepped down amid a sex assault scandal in 2011.
