The aim of mindfulness training in Buddhist teachings is to cultivate an objective appraisal of the nature of experiential phenomena to increase one’s understanding of the causes and maintenance of suffering. The Mindfulness-based Self-Efficacy Scale (MSES) was initially constructed to assess changes in perception of self-efficacy in clinical populations undertaking mindfulness training as part of therapy. The MSES-R is composed of 22 items and six factors (Emotional Regulation, Equanimity, Social Skills, Distress Tolerance, Taking Responsibility, and Interpersonal Effectiveness). For the past two decades, several clinical and nonclinical studies have reported that the MSES-R shows good sensitivity to change over the course of mindfulness-based therapy programs including in heterogenous clinical samples. Psychometric studies have demonstrated good validity and reliability of the MSES-R. A recent confirmatory factor analysis performed on two Australian samples, two Canadian samples, and one Australian university student sample indicated adequate fit across all samples, although factors containing fewer items had low reliability. The MSES-R displayed scalar measurement invariance between the clinical and community Australian samples, and across the Australian and Canadian samples. In this and other studies, community samples score significantly higher on the MSES-R than clinical samples. Respondents who regularly engaged in meditative or contemplative practices also score higher on the MSES-R than nonmeditators. The MSES-R is a useful mindfulness-based assessment tool to investigate the efficacy and outcomes of mindfulness-based programs implemented in both clinical and nonclinical settings.