Objectives <p>This study aimed to perform the cross-cultural adaptation and psychometric validation of the Mindfulness Adherence Questionnaire (MAQ) for the Brazilian context, in order to offer an adequate instrument to measure adherence to mindfulness practice in mindfulness-based interventions.</p> Method <p>The adaptation process followed international guidelines for translation and semantic equivalence, including translation-back-translation methodology, review by an expert committee, and application in a pilot study. A convenience sample composed of 303 participants (82.61% women), aged between 22 and 73 years, was recruited online. Participants completed the Brazilian versions of the MAQ, Depression, Anxiety and Stress Scales (DASS-21), Big Five Inventory (BFI), Mindful Attention Awareness Scale (MAAS), and Five Facet Mindfulness Questionnaire (FFMQ). Construct validity was assessed through exploratory factor analysis (EFA) and confirmatory factor analysis (CFA). Reliability was analyzed using Cronbach's alpha and omega coefficients.</p> Results <p>The factor structure showed good adequacy, with satisfactory factor loadings. Internal consistency measures were adequate. The MAQ showed positive correlations with all variables related to mindfulness and personality traits, except for anxiety and stress scores.</p> Conclusions <p>The Brazilian version of the MAQ demonstrated acceptable psychometric properties and the preliminary findings suggest that the MAQ shows promising evidence of validity and reliability to assess the quantity and quality of formal and informal mindfulness practice, contributing to research and the integrity of clinical practice in Brazil.</p> Preregistration <p>This study is not preregistered.</p>