The benefits of empirically supported mindfulness-based programs (MBPs) are well documented, but the potential for harm has not been comprehensively studied. The available literature, although too small for a systematic review, suggests that the question of harm in MBPs needs careful attention. We argue that greater conceptual clarity will facilitate more systematic research and enable interpretation of existing findings. After summarizing how mindfulness, mindfulness practices, and MBPs are defined in the evidence-based context, we examine how harm is understood and studied in related approaches to physical or psychological health and wellbeing, including psychotherapy, pharmacotherapy, and physical exercise. We also review research on harmful effects of meditation in contemplative traditions. These bodies of literature provide helpful parallels for understanding potential harm in MBPs and suggest three interrelated types of factors that may contribute to harm and require further study: program-related factors, participant-related factors, and clinician- or teacher-related factors. We discuss conceptual issues and empirical findings related to these factors and end with recommendations for future research and for protecting participants in MBPs from harm.