Objectives <p>This review examined why personal mindfulness practice is regarded as foundational for teachers delivering mindfulness-based interventions (MBIs), particularly Mindfulness-Based Cognitive Therapy (MBCT) and Mindfulness-Based Stress Reduction (MBSR). Although professional standards mandate sustained personal practice, empirical findings linking teacher competence or embodiment to participant outcomes remain inconsistent. The review aimed to synthesise evidence examining relationships between personal practice, embodiment, teaching competence, and participant outcomes.</p> Method <p>A systematic search of PsycINFO, MEDLINE, PubMed, Web of Science, and CINAHL was conducted for studies published between 2010 and 2025. Eligible studies examined teacher-related variables within MBCT or MBSR. Quantitative, qualitative, mixed-methods studies, and professional guidelines were included. Data were synthesised using a narrative synthesis approach due to the heterogeneity of designs, measures, and outcomes.</p> Results <p>Seventy-two publications met inclusion criteria. Quantitative studies reported mixed associations between assessed teacher competence and clinical outcomes. In contrast, qualitative studies consistently emphasised teacher embodiment, relational presence, and authenticity as central to participant experience. Mixed-methods and training studies suggested improvements in teacher interoceptive awareness and emotional regulation following extended training, although links to participant outcomes remained unclear.</p> Conclusions <p>While direct associations between teacher competence and symptom change remain inconsistent, converging evidence supports prioritising personal practice as foundational for cultivating embodiment and relational presence. These qualities appear central to ethical and effective teaching and warrant continued emphasis in mindfulness teacher training and future research.</p> Preregistration <p>This study is not preregistered.</p>