Introduction: The mandatory reporting (MR) of mesotheliomas, established by the French Institute for Public Health Surveillance, aims to strengthen the surveillance of mesotheliomas (all sites, nationwide) and to improve understanding of asbestos exposure in three poorly studied populations: women, men under 50 years of age, and individuals with extrapleural mesothelioma. Materials and Methods: Since January 2012, every physician (pathologists and clinicians) practicing in France who diagnoses mesothelioma must report it to the Regional Health Agency. The completeness estimate for pleural mesotheliomas was calculated by comparing data with that from the National Mesothelioma Surveillance Program (PNSM), which covered 21 departments in 2013, over the same period. Results: The 1,282 new cases in 2012 and 2013 were reported between January 2012 and April 2014 by a pathologist (76%) and/or a clinician (52%). The tumor was located in the pleura (86%), the peritoneum (8%), and, in 6% of cases, at other sites. The sex ratio was 2.4. The average completeness rate for pleural mesotheliomas in the departments covered by the PNSM was 46% in 2012, with significant regional disparities. Conclusion: The characteristics of the reported cases are similar to those in the literature. Coverage rates for 2012 and 2013 indicate good physician compliance despite regional disparities. The DO and the PNSM are part of the national epidemiological surveillance system for mesotheliomas supported by the 2014–2019 Cancer Plan.