Firefighters' perceptions of mental health can inform management. This qualitative study explored Canadian career firefighters' experiences, needs, and research priorities with respect to mental health. Thirty-nine career firefighters (33 men, 6 women) of different ranks and geographic locales were interviewed using a semi-structured interview guide. The interviews were recorded, transcribed, and qualitatively analyzed using thematic analysis within an interpretive description approach. Firefighters reported that critical incidents and chronic job stressors contributed to mental health symptoms that led to burnout, compassion fatigue, and mental and physical injury. They were concerned with family impacts, like lack of full openness, reduced financial stability, and risk of divorce; and work impacts, like interpersonal conflict, lack of support to fellow firefighters, task avoidance, and absenteeism. A broad array of barriers and facilitators were found in firefighter work, culture, programs, social supports, health care, and societal factors. Variability in access to help, the changing fire service, and the complexity of knowing what to do to achieve mental health were evident across themes. Firefighters identified the need for research in four areas: awareness and monitoring, understanding etiology of mental health, better prevention and treatment, and access to care. Across domains of inquiry, context, "two sides to the coin", and uncertainty were overarching themes.