The job of a firefighter involves constant exposure to trauma and work with casualties. Nonetheless, as a group, they are neglected in stress research. Several studies deal with the impact of stress on the lives of firefighters, but few take into account that the positive and negative outcomes of stress can occur simultaneously and independently of each other. The aim of this study was to examine the predictor contribution of social support at work and in the family, self-efficacy and mindfulness in explaining the professional quality of life of firefighters. These constructs were proved to be related to stress and they can be affected by intervention. In this research, 125 firefighters took part in completing a battery of questionnaires consisting of the Demographic Questionnaire, the Social Support at Work and Family Scale (Šimunić, Gregov i Proroković, 2016), The Mindfulness Awareness Attention Scale (Brown i Ryan, 2003), the General Self-Efficiency Scale (Schwarzer i Jerusalem, 1995), and the Professional Quality of Life Questionnaire (Stamm, 2010). The results of the analysis showed that significant positive predictors of compassion satisfaction are self-efficacy and social support of colleagues. Furthermore, a significant negative predictor of secondary traumatic stress is mindfulness and a significant negative predictor of burnout syndrome is self-efficacy. There was also a significant positive association of perceived social support of partners with compassion satisfaction and a significant negative association with secondary traumatic stress in those participants who are married. Finally, the implications of the results were discussed and suggestions for future research on the professional quality of life of firefighters were offered. The research findings could be used to design successful proactive interventions to increase the professional quality of life of firefighters in Croatia.