Prior research suggests mindfulness-based interventions effectively reduce stress in trainee psychologists, enhance wellbeing and cultivate clinical skills and competencies. This study explored how trainee school psychologists perceived the effects of a mindfulness-based intervention on their development as psychologists. Forty trainee school psychologists participated in a 6-week online mindfulness-based intervention. They completed weekly written reflective journals throughout the programme which were later analysed using thematic analysis. Four core themes were identified: (1) changes in awareness and attention; (2) enhanced wellbeing; (3) commitment to ongoing personal practice and (4) cultivation and enhancement of professional development. Participants (n = 24) who completed the mindfulness workshop during the COVID-19 pandemic indicated that mindfulness practice was particularly useful for managing uncertainty and other related stressors. It was concluded that practicing mindfulness supported trainee school psychologists' personal and professional development, particularly related to compassion, resilience and therapeutic presence.