Background: In recent years, third-wave therapies have risen to prominence. Research into adapting and evaluating third-wave therapies for adults with intellectual disabilities has identified that third-wave therapies are accessible, acceptable, and effective (improving a range of symptoms and skills). Method: This meta-ethnography followed Noblit and Hare's approach to synthesising findings from qualitative studies to examine how adults with intellectual disabilities experience third-wave therapy groups. A systematic review of three databases identified 13 studies that met our inclusion criteria. Results: We identified that third-wave therapy groups can be a 'Transformational' process for adults with intellectual disabilities that involves three stages: 'Concealment', 'Opening up' and 'Flourishing'. Conclusion: Findings highlight the importance of therapeutic processes; especially, working with defences, and developing and maintaining safety/trust. Recommendations include the development of an objective measure of group safety/trust.