Objectives: This study examined a cognitive stress-moderation model that posits that the harmful effects of chronic stress are decreased in police officers who perceive high levels of physical fitness. It also determined whether the stress-buffering effect of perceived fitness is influenced by officers' self-reported sleep. Methods: A total of 460 police officers (n=116 females, n=344 males, mean age: M=40.7; SD=9.7) rated their physical fitness and completed a battery of self-report stress, mental health, and sleep questionnaires. Three-way analyses of covariance were performed to examine whether officers' self-reported mental health status depends on the interaction between stress, perceived fitness and sleep. Results: Highly stressed officers perceived lower mental health and fitness and were overrepresented in the group of poor sleepers. Officers with high fitness self-reports revealed increased mental health and reported good sleep. In contrast, poor sleepers scored lower on the mental health index. High stress was more closely related to low mental health among poor sleepers. Most importantly, perceived fitness revealed a stress-buffering effect, but only among officers who reported good sleep. Conclusions: High perceived fitness and good sleep operate as stress resilience resources among police officers. The findings suggest that multimodal programs including stress management, sleep hygiene and fitness training are essential components of workplace health promotion in the police force.(J Occup Health 2013; 55: 376-384)