Mélanie Guérin, 35, who lives in the western French town of Nantes, should have caught a flight back after a month in Nepal on 12 August but never arrived home, announcements on social media say.
"We were notified by the Nepalese authorities of the disappearance of Frenchwoman on 13 August," the ministry said. "We are in contact with the missing person's family and fully mobilised, along with the Nepali police, to find her."
After staying several days in the town of Pokhora, Guérin checked out of her hotel to take a bus to the village of Lumbini, 180 kilometres away.
She was taking part in the Wwoof scheme, which finds people places to stay in return for work on organic farms.
Her bag along with her papers, her plane ticket and her diary of the holiday were found at the side of the road.