BACKGROUND: Police officers experience a high degree of chronic stress. Policing ranks among the highest professions in terms of disease and accident rates. Mental health is particularly impacted, evidenced by elevated rates of burnout, anxiety and depression, and poorer quality of life than the general public. Mindfulness training has been shown to reduce stress, anxiety, burnout and promote quality of life in a variety of settings, although its efficacy in this context has yet to be systematically evaluated. Therefore, this trial will investigate the efficacy of a mindfulness-based intervention versus a waitlist control in improving quality of life and reducing negative mental health symptoms in police officers. METHODS: This multicenter randomized controlled trial has three assessment points: baseline, post-intervention, and six-month follow-up. Active police officers (n = 160) will be randomized to Mindfulness-Based Health Promotion (MBHP) or waitlist control group at two Brazilian major cities: Porto Alegre and São Paulo. The primary outcomes are burnout symptoms and quality of life. Consistent with the MBHP conceptual model, assessed secondary outcomes include perceived stress, anxiety and depression symptoms, and the potential mechanisms of resilience, mindfulness, decentering, self-compassion, spirituality, and religiosity. DISCUSSION: Findings from this study will inform and guide future research, practice, and policy regarding police offer health and quality of life in Brazil and globally. TRIAL REGISTRATION: ClinicalTrials.gov NCT03114605 . Retrospectively registered on March 21, 2017.