Background: Evidence concerning workplace bullying as a risk factor for mental disorders is currently limited to depressive disorders and mainly based on non-clinical assessments. This study aims to examine the prospective association of self-reported workplace bullying with different types of register-based hospital-diagnosed mental disorders and redeemed psychotropic drug prescriptions. Methods: Using a cohort study design, we examined a pooled dataset of 75,252 participants from 14 questionnaire-based surveys conducted between 2004 and 2014. In the questionnaires, workplace bullying was measured by a single item. The questionnaires were linked to Danish registers on hospital-diagnosed mental disorders and redeemed psychotropic drug prescriptions up to 2016. Data were analysed by multivariate Cox proportional hazard models, including only participants without a history of mental disorders or prescriptions since 1995. Results: After adjustment for sex, age, marital and socio-economic status, workplace bullying was associated with an excess risk of any mental disorder (HR 1.37; 95 % CI: 1.17–1.59) as well as mood disorders and neurotic, stress-related, and somatoform disorders. In stratified analyses, this association were statistically significant only among women. Workplace bullying was also associated with any psychotropic drug prescription (fully-adjusted HR 1.43; 95 % CI: 1.35–1.53). This association was observed in both sexes and for all prescriptions, including anxiolytics, hypnotics and sedatives, antidepressants, and nootropics. Limitations: Firm conclusions about sex-related differences cannot be drawn. Residual confounding by unmeasured factors such as personality cannot be ruled out. Conclusions: Workplace bullying was associated with higher risks of diagnosed mental disorders among women and psychotropic drug prescriptions in both sexes.