This research introduces the "Mindfulness Mindset Scale," a concise and reliable tool designed to measure beliefs about the malleability of mindfulness skills. Study 1 (N = 285) revealed a single-factor structure through exploratory factor analysis, further validated in Study 2 (N = 286) using confirmatory factor analysis. Studies 3a (N = 266) and 3b (N = 320) revealed associations between the Mindfulness Mindset Scale and other measures of mindset, trait mindfulness, and coping, showing reasonable convergent and divergent validity. Study 4 (N = 470) showed the predictive validity of the mindfulness mindset, being correlated with behavioral persistence, effort, resilience, challenge-seeking, and academic grades. Study 5 (N = 320) supported the academic correlates of malleable beliefs of mindfulness beyond the mental health factors from Study 3 in two countries. In Study 6 (N[subscript French] = 613, N[subscript Hungarian] = 524), we demonstrated that a well-established learning mindset intervention can lead to changes in mindfulness mindset in two national contexts. Finally, a brief mindfulness mindset intervention designed for Study 7 (N = 208) also led to changes in malleability beliefs about mindfulness skills. These behavioral results suggest that beliefs about mindfulness being malleable are a novel construct distinct from trait mindfulness. Such beliefs are related to adaptive psychological mechanisms relevant in educational contexts, considering students' coping, mastery behavior, and academic performance. Importantly, these beliefs can be modified by brief interventions.