However, the judges did not hand down any sentence in the case.
The IMF chief was facing charges linked to a €404m (£340m) payment made to French business tycoon Bernard Tapie in 2008, when Lagarde was finance minister under former President Nicholas Sarkozy.
The court ordered her to face trial for her role in the payout in December last year, an order she appealed - however, in July the appeals court ruled that Lagarde would have to participate in a trial.
The IMF said it would stand behind Lagarde as she went through the trial process.
Her lawyer said immediately after this afternoon's ruling that his team would look into appealing the decision.
The case concerns a payment made to Tapie to settle a commercial dispute the businessman was in with the government.
The settlement is alleged to have been rigged because of Tapie's support of then-president Nicolas Sarkozy.
Lagarde, who was finance minister at the time, has insisted throughout that she is innocent of accusations that she played an "improper" role in the arbitration process.