Purpose The study's objective was to examine whether and how mindfulness training and practice might impact indicators of three capacities identified as critical for leading in the twenty-first century: resilience, leading in complex contexts and collaboration. Design/methodology/approach We conducted a non-randomised wait-list controlled study with 57 senior leaders (81 per cent female) who undertook an eight-week “Mindful Leader” programme. Findings Our findings suggest the programme was effective in developing leaders in terms of their mindfulness, resilience and self-perceived leadership competencies such as collaboration and agility in complex situations. The amount of mindfulness practice the leaders undertook was associated with improvements in mindfulness, resilience and collaboration. Furthermore, participants reported that the programme was beneficial for them as leaders and that the training format was feasible. However, objective measures of cognitive functioning and leadership competence did not improve significantly within the mindfulness intervention group. Practical implications Mindfulness practice may be a promising and effective method for leader development. Our results suggest that mindfulness can be learnt and developed by executive leaders, as long as they practice for at least 10 min per day. Originality/value This is the first study to investigate how resilience, leading in complex contexts and collaboration can be developed through mindfulness training.