Introduction - On November 14, 2018, an outbreak of dermatophytosis was reported at a preschool in Maine-et-Loire, with more than 15 cases since the start of the school year. Epidemiological, microbiological, and environmental investigations were conducted. Materials and Methods - A repeated cross-sectional study was conducted among the school’s 109 students and 10 adults. An initial questionnaire-based survey was conducted on-site on November 30, combined with a classroom visit. Mycological samples were collected from lesions and from floor mats. Active case finding with clinical screening was subsequently conducted until January 18, 2019. Results - Over the study period, 35 students and 3 adults became ill. The overall prevalence was 35% (38 out of 109 individuals seen and/or examined) and decreased with age, ranging from 53% among children under 4 years old to 17% among those aged 5 and older. Lesions were predominantly located on the upper body (85%) and presented as circinate epidermophytosis in three-quarters of cases. Sleeping arrangements were identified as a likely source of indirect contamination. The anthropophilic dermatophyte Trichophyton tonsurans was isolated in 21 cases and on 16 of the 18 rest mats sampled. Discussion - T. tonsurans is a resurgent species in mainland France, warranting increased vigilance. Preventive measures, including information and awareness-raising for parents, teachers, and healthcare professionals, should be strengthened in all public and private institutions that care for children (schools, recreation centers).