Firefighters are routinely exposed to potentially traumatic events, making them vulnerable to debilitating mental health problems. Consequently, promoting well-being and the ability to respond effectively and safely to work demands are vital. The FIRE is an innovative mindfulness, Acceptance and Commitment Therapy, and compassion-based manualized intervention encompassing eight weekly group sessions delivered at Fire Stations. A preliminary version of this program will be refined based on qualitative inputs from structured interviews with firefighters and emergency/civil protection sector stakeholders. The FIRE feasibility dimensions of adaptation, acceptability, implementation, practicality, integration, and limited efficacy will be evaluated in a two-arm, 1:1, non-blinded randomised controlled trial. The extent to which the FIRE contributes to the promotion of well-being and the decrease of psychopathological symptoms, and the causal theory underlying FIRE, will be explored through an examination of potential mechanisms of change.