Rationale: Previous research with emergency service workers has examined the relationship between operational and organizational stress and negative indicators of mental health, and generally found that organizational stress is more strongly related to pathology than operational stress. Method: The current study aimed to create and test a model predicting both posttraumatic stress disorder (PTSD) symptoms and posttraumatic growth (PTG) simultaneously in a sample of firefighters (N = 250). Results: The results found that the model demonstrated good fit for the data. In contrast to previous research operational stress was directly related to PTSD symptoms, whereas organizational stress was not. Organizational stress was indirectly related to PTG, through the mediating role of organizational belongingness. Conclusion: This research identified organizational belongingness as a good target for psychosocial interventions aimed at promoting positive adaptation following the experience of trauma in emergency services.