Purpose: This study was conducted to identify factors which influence mental health of firefighters. Methods: Participants in this study were firefighters from D city who were doing activities like extinguishing fire or rescuing sufferer at fire or accident scenes. A survey was conducted from September14 to 24, 2010. Research tools were perception of job stress, problems-focused coping, seeking social support, emotion-focused coping, and wishful thinking coping which are sub-domain of coping stress, and SCL-90-R. Data were analyzed using SPSS/WIN 14.0, and included t-test, one-way ANOVA, and Scheffe back-testing. Pearson`s correlation coefficient and stepwise multiple regression were also conducted to identify factors influencing mental health. Results: Mental health was positively correlated with perception of job stress, emotion-focused coping, and wishful thinking coping. Effective variables were perception of job stress (β=38, p<.001), emotion-focused coping (β=28, p<.001), and problem-focused coping (β=-.15, p=.012). These variables explained 26% of the variance in mental health. Conclusion: The results suggest that improvements in problem-focused coping and decreases in perception of job stress and emotion-focused coping are important in promoting the mental health of firefighters.