In early May 2022, cases of Mpox were reported in Europe and around the world, with no direct link to travel to Central or West Africa—where the virus is present—or to people returning from travel. The majority of these cases involved men who have sex with men (MSM). From the very beginning, Santé publique France mobilized its Sexosafe initiative to alert the MSM population and disseminate targeted prevention messages. As part of a phased communication plan, two campaigns focusing on symptom recognition and vaccination promotion were launched from June 9, 2022, to September 30, 2022, generating 884,071 visits to the sexosafe.fr website. In the context of public health emergencies, prevention efforts among populations vulnerable to epidemics are greatly facilitated by the existence of sustainable social marketing initiatives based on survey data, a network of nonprofit partners, and healthcare professionals.