Background: Mindfulness-based interventions have been shown to be effective in the treatment of a range of health and psychological disorders in adults and young people without intellectual disabilities (ID). Clinical studies are emerging reporting on the efficacy of mindfulness-based interventions as a stand-alone treatment for common clinical disorders in adults with ID. Method: This paper aims to evaluate the efficacy of an innovative structured mindfulness-based cognitive therapy (MBCT) group programme adapted for adults with ID with a diagnosis of either recurrent depression, anxiety or both clinical conditions and a history of deliberate self-harm behaviour. Two groups ran consecutively consisting of a total of fifteen participants and seven carers. All participants were recorded as having either a borderline, mild, or moderate ID. The group programme ran over a period of 9 weeks with a follow-up session at 6 weeks post group intervention. Outcome measures included the Hospital Anxiety and Depression Scale and two sub-scales from the Self-Compassion Scale administered at baseline, post therapy and at 6-week follow-up. Results: The evaluation showed that participants reported an improvement in their experience of depression, anxiety, self-compassion and compassion for others. The most significant impact was in the reduced levels of anxiety reported. Improvements across all outcomes were maintained at 6-week follow-up. Conclusion: The results of the evaluation suggest that people with intellectual disabilities benefit from a structured MBCT group intervention and the results are maintained at 6-week follow-up.