Introduction: Support staff working with individuals with intellectual disability (ID) and challenging behaviour experience high levels of work-related stress. Preliminary theoretical and experimental research has highlighted the potential suitability of acceptance and mindfulness approaches for addressing support staff stress. This study examines the effectiveness of an acceptance and mindfulness-based stress management workshop on the levels of psychological distress and well-being of support staff working with individuals with ID and challenging behaviour. Method: Support staff (n=120) were randomly assigned to a workshop intervention condition (n=66) or to a waiting list control condition (n=54). Measurements were completed at three time points (pre-, post and six week follow-up) for: psychological distress, well-being, perceived work stressors, thought suppression, emotional avoidance/psychological inflexibility. Results: The results showed that for psychological distress there was a significant interaction effect in favour of the workshop. Thought suppression was found to reduce significantly in the intervention group post to follow-up, although no significant change was found in wellbeing or experiential avoidance/psychological inflexibility. For individuals with higher levels of psychological distress at pre-intervention (GHQ>11), larger effect sizes for the interaction were found, suggesting a greater impact of the workshops on the most distressed. Conclusion: Overall, results demonstrated support for the effectiveness of an acceptance and mindfulness-based intervention in reducing distress.