This chapter examines how human factors influence firefighter safety, performance, and decision-making under pressure. Drawing on human systems engineering, aviation psychology, and trauma-informed leadership, it explores the intersection of stress, fatigue, cognitive load, communication breakdowns, and organizational culture in shaping outcomes both on and off the fireground. The chapter challenges blame-oriented models of incident review. It introduces psychologically informed frameworks, such as just culture and human factors analysis, to better understand near misses, critical incidents, and everyday errors. Emphasizing that operational failures are rarely due to incompetence alone, it advocates for systemic prevention strategies that take into account human limitations. Practical applications include integrating human factors into after-action reviews, leadership training, and the design of wellness programs. The chapter emphasizes the importance of psychological literacy among officers and clinicians alike in developing safer, more resilient fire service systems.