Leptospirosis is a zoonotic disease endemic to most countries in the Indian Ocean region. In Mayotte, surveillance has been stepped up since 2008, notably through the systematic reporting to the Indian Ocean Health Agency of all cases confirmed by PCR (Polymerase Chain Reaction) by the laboratory at the Mayotte Hospital Center (CHM). In 2016, a large-scale outbreak was observed during the hot and humid season, from January to April. In total, over the course of the year, 152 locally acquired cases and 3 imported cases were recorded, including 144 between January and May. The annual incidence was 65 cases per 100,000 inhabitants. As in previous years, this disease primarily affected men (three-quarters of cases) in their thirties engaged in high-risk activities (agriculture, livestock farming). Children and adult women were affected in significant proportions (26% and 19%, respectively). Walking barefoot (77%) and exposure to water from rivers, swamps, or mud puddles (86%) were frequently reported among cases. The peak in cases followed the peak in rainfall, but with a shorter lag time than in other years: between 1 and 2 months. The predominant serogroup remained the Mini serogroup, accounting for more than 70% of the strains typed in 2016. This confirms the atypical nature of the microbial epidemiology of leptospirosis in Mayotte, with no strains of the Icterohaemorragiae serogroup identified. Leptospirosis remains a significant public health problem on the island of Mayotte. Human exposure results from environmental contamination during the rainy season, which was particularly heavy in the first quarter of 2016. Health education and prevention initiatives targeting at-risk populations, as well as those focused on young people—who make up more than half of the island’s inhabitants—are essential to help the population understand the disease and its risk factors. At the same time, certain comprehensive measures are essential to combat leptospirosis in Mayotte: improving housing sanitation, wastewater management, and household waste management, and ensuring universal access to drinking water.