Mental disorders are a frequent cause of morbidity and sickness absence in working populations; however, the status of psychiatric sickness absence as a predictor of mortality is not established. The authors tested the hypothesis that psychiatric sickness absence predicts mortality from leading medical causes. Data were derived from the French GAZEL cohort study (n = 19,962). Physician-certified sickness absence records were extracted from administrative files (1990–1992) and were linked to mortality data from France's national registry of mortality (1993–2008, mean follow-up: 15.5 years). Analyses were conducted by using Cox regression models. Compared with workers with no sickness absence, those absent due to psychiatric disorder were at increased risk of cause-specific mortality (hazard ratios (HRs) adjusted for age, gender, occupational grade, other sickness absence—suicide: 6.01, 95% confidence interval (CI): 3.07, 11.75; cardiovascular disease: 1.84, 95% CI: 1.10, 3.08; and smoking-related cancer: 1.65, 95% CI: 1.07, 2.53). After full adjustment, the excess risk of suicide remained significant (HR = 5.13, 95% CI: 2.60, 10.13) but failed to reach statistical significance for fatal cardiovascular disease (HR = 1.59, 95% CI: 0.95, 2.66) and smoking-related cancer (HR = 1.31, 95% CI: 0.85, 2.03). Psychiatric sickness absence records could help identify individuals at risk of premature mortality and serve to monitor workers’ health.