Introduction – Employees of the Régie autonome des transports parisiens (RATP) are exposed to a wide range of occupational hazards and stressors. The objectives of this study were to compare overall and cause-specific mortality among current and former RATP employees with that of the general population of Île-de-France and to conduct an analysis by occupation. Materials and Methods – All employees who worked at the RATP between January 1, 1980, and December 31, 2012, and who had at least one year of service were included in the study. When unknown, the employee’s vital status was obtained from the National Directory of Natural Persons (RNIPP). The initial causes of death for deceased employees were obtained from the Center for Epidemiology on Medical Causes of Death (CépiDc). They were classified according to the nomenclature of the European Summary List of Causes of Death. Employees’ career histories were reconstructed from the time of their entry into the company, and the various job categories were grouped into 22 categories. Overall mortality and mortality by cause among employees was compared to that of the general population of Île-de-France by calculating standardized mortality ratios (SMR). Mortality by socio-professional category (SPC) was compared to that of the corresponding SPC in mainland France. A Cox model was used to calculate the relative risk of death according to occupation. Results – The cohort consists of 96,634 employees, including 78,702 men and 17,932 women. As of December 31, 2012, 11,466 (14.6%) men and 1,174 (6.5%) women had died. All-cause mortality was significantly lower than that of the general population of the Île-de-France region: SMR = 0.94 (95% confidence interval, 95% CI: [0.93–0.96]) among men, 0.91 [0.86–0.97] among women. Unlike other occupational categories, white-collar workers showed excess mortality among men (1.15 [1.10–1.21]) and among women (1.12 [1.04–1.21]). Across all occupations, kidney cancer (1.24 [1.03–1.48]), acute myocardial infarctions (1.17 [1.08–1.26]), cirrhosis, chronic fibrosis and hepatitis (1.11 [1.01–1.21]), as well as suicides and self-inflicted injuries (1.20 [1.08–1.32]) were significantly higher causes of death among men compared to the reference population. Among women, a significant excess mortality from transportation accidents was observed (1.85 [1.22–2.69]). Analyses by occupational group revealed higher risks of death in certain groups (such as unskilled maintenance workers, station agents) and, additionally, excess causes of death among workers in specific occupational groups (notably pleural tumors among skilled maintenance workers or ischemic heart disease among bus drivers, security guards, and unskilled maintenance workers). Conclusion – These results call for strengthening targeted prevention measures implemented within the company for employees in the occupations identified in this study in order to reduce the observed inequalities. A new analysis incorporating more recent data will increase statistical power and update the results.