Given the demanding nature of many professions, efforts are ongoing to develop initiatives to improve occupational wellbeing, including mindfulness-based interventions (MBIs). To assess the efficacy of MBIs, meta-analytic procedures were conducted on 35 randomized controlled trials derived from an earlier inclusive systematic literature search (covering all occupations, MBIs, and wellbeing-related outcomes). Mindfulness had significant moderate effects on deficit-based outcomes such as stress (SMD = -0.57), anxiety (SMD = -0.57), distress (SMD = -0.56), depression (SMD = -0.48), and burnout (SMD = -0.36), and significant moderate to small effects on asset-based outcomes like health (SMD = 0.63), job performance (SMD = 0.43), compassion and empathy (SMD = 0.42), mindfulness (SMD = 0.39), and positivewellbeing (SMD = 0.36), while no significant effects were observed for depression or emotional regulation. However, the quality of the studies was inconsistent, suggesting more high-quality randomised controlled trials are needed.