Francesca Peirotti, 31, was given a six-month suspended sentence and banned from entering the French département of Alpes-Maritime, which borders Italy, for five years, a stiffer sentence than the 1,000-euro fine she was appealing against.
She is an activist with the Habitat et Citoyenneté group, which is based in Alpes-Maritime.
In 2016 she picked up eight Eritreans, including a baby, on a carpark in Vintimille, on the Italian side of the border, and took them into France in a van marked "Urgence Sociale Croix-Rouge" (Social emergency Red Cross).
A joint patrol of French and Italian police stopped her in France and she was charged with helping the illegal entry of foreigners to France, as well as possession of drugs.
Her defence was that she was acting for humanitarian purposes but the court rejected her argument that the Eritreans' security and dignity would be infringed in Italy.
Her lawyer, Zia Oloumi, told the AFP news agency that she intends to take the case to the Court of Cassation, as have two other migration activists, Pierre-Alain Mannoni and Cédric Herrou.
France's Constitutional Council this month ruled that people who helped migrants for humanitarian reasons within France could not be prosecuted.
But it said that helping them cross the border, even if it was not for personal profit, would remain an offence.