Firefighters are repeatedly exposed to potentially traumatic events and occupational stressors that place them at heightened risk of post-traumatic stress disorder (PTSD), depression, anxiety and impaired quality of life. Despite evidence linking dysfunctional coping and metacognition to emotional disorders, little is known about these factors in firefighters. This study aims to examine levels of PTSD, depression, anxiety, quality of life and well-being among Spanish specialist firefighters, and to identify the role of metacognitive beliefs and coping strategies in these outcomes. A cross-sectional survey will recruit approximately 220 active firefighters from several Spanish fire services through the International Association of Firefighters and Emergency Psychology. Participants will complete validated Spanish versions of the PCL-5 (PTSD), BDI-II (depression), BAI (anxiety), MCQ-30 (metacognition), Brief-COPE (coping), Pemberton Happiness Index (well-being) and Brunnsviken Brief Quality of Life Scale (quality of life). Multiple regression analyses will test associations between metacognition, coping styles, trauma exposure and mental-health outcomes, controlling for sociodemographic and occupational variables. We hypothesize that: (1) a significant proportion of firefighters will show clinically relevant PTSD, depression, and anxiety symptoms, this proportion will be higher than that of the general population; (2) dysfunctional metacognitive beliefs and avoidance-focused coping will predict higher symptomatology and lower quality of life, and (3) emotional numbing, hypervigilance and hyperarousal symptom clusters will be most strongly associated with diminished well-being. Identifying and validating modifiable psychological factors, such as metacognition and coping strategies, could inform preventive and therapeutic interventions, enhance occupational health policies, and improve resilience among first responders.