General practitioners (GP), on the frontline for individuals with mental health problems, often deal with work-related common psychiatric disorders. We aimed to determine the prevalence of work-related common psychiatric disorders in general practice and associated patients" and GPs" characteristics. HERACLES, a cross-sectional study among 2019 working patients of 121 GPs in the Nord - Pas-de-Calais region in France. Common psychiatric disorders were assessed using the MINI International Neuropsychiatric Interview, patient-perceived psychological distress and GP-diagnosed psychiatric disorders. The work-relatedness of common psychiatric disorders was ascertained by the GP and/or the patient. Prevalence rates adjusted on age were calculated by sex and associated characteristics were ascertained using multilevel Poisson regression models. The prevalence of work-related common psychiatric disorders ascertained using the MINI was estimated at 25.6% [23.7-27.5], 24.5% [22.6-26.4] for self-reported psychological distress and 25.8% [23.9-27.7] for GP-diagnosed psychiatric disorders. Age, history of psychiatric disorders, consultation for psychological purpose and GP's characteristics were associated with MINI-identified psychiatric disorders. The prevalence of work-related common psychiatric disorders among working adults seen in general practice is high but further studies are needed to support this results.