Background: Hospitals, police stations, and fire departments are highly demanding workplaces. Staff members are regularly exposed to various stressors including traumatic events. Correspondingly, several studies report high rates of mental health issues among these occupations. Nevertheless, despite these challenging circumstances, some staff members manage to sustain their mental health. The current study is the first to investigate three healthpromoting factors simultaneously among three different, highly demanding occupations. Methods: The present cross-sectional survey investigated health-promoting factors (sense of coherence-SOC, trait-resilience, locus of control-LOC) and mental health outcomes (general psychopathological symptom burden, posttraumatic stress, burnout) in medical staff (n = 223), police officers (n = 257), and firefighters (n = 100). Results: Among all occupations, SOC, trait-resilience, and an internal LOC were negatively associated with general psychopathological symptoms, posttraumatic stress, and burnout symptoms. By contrast, all these outcome measures were positively correlated with an external LOC. Multiple regression models including all healthpromoting factors explained 56% of the variance in general psychopathological symptoms and 27% in posttraumatic stress symptoms. Among all occupations, SOC was the strongest predictor of both general psychopathological symptom burden and posttraumatic stress symptoms. Multigroup path analyses revealed minor differences across occupations, mainly driven by a stronger influence of LOC in police officers. Conclusion: Across all occupations, SOC was identified as the most important health-promoting factor. Future longitudinal studies should further examine the causal link between health-promoting factors and mental distress in different workplaces. Such studies will also allow for further development and evaluation of resilience promoting programs.