Objectives - On Saturday, February 20, 2010, firefighters in the Hérault department reported to the Hérault Territorial Delegation of the Regional Health Agency (DT34-ARS) that approximately 15 people had experienced abdominal pain, nausea, and vomiting after consuming a cocktail served during a rugby match at the Yves du Manoir Stadium in Montpellier. Methods - The investigation into this report was conducted jointly by the health surveillance teams of the ARS and the Languedoc-Roussillon Interregional Epidemiology Unit (Cire LR) to confirm the incident, identify the source of contamination, and guide management measures. A case-control study was conducted using a standardized questionnaire. Concurrently, laboratory analyses and a veterinary investigation were carried out, including sampling of control dishes and inspection of the caterer’s premises and the stadium. Results - A total of 94 cases and 110 controls were identified among the cocktail party attendees. The epidemiological investigation revealed two waves of the outbreak, one early and the other later, with distinct symptoms and median incubation periods of 3.5 hours and 30 hours, respectively. The results of the epidemiological, biological, and veterinary investigations supported the hypothesis that the early cases were poisoned by ingesting mini ham hocks contaminated with Staphylococcus aureus (OR: 3.75; 95% CI [1.91–7.35], p = 0.001) and food poisoning in the late-onset cases due to consumption of oysters contaminated with norovirus (OR: 32.22; 95% CI [7.09–146.34], p < 0.001). Conclusion - This investigation identified the foods and pathogens responsible for this outbreak of foodborne illness. This incident underscored the importance of adhering to hygiene practices in institutional food service and of implementing early control measures as soon as the results of epidemiological or veterinary investigations are known. (R.A.)