Background: There is little research that has examined what support strategies are effective to help adults with intellectual disabilities take their prescribed medication correctly. The aim of the study was to gain an understanding of the barriers and supports that contribute to adults with intellectual disabilities self-managing their prescribed medicines. Methods: Nine adults with intellectual disabilities and two support staff participated in this two-phase study. Phase 1 consisted of focus groups and Phase 2 involved participants taking part in simulated real-world scenarios based on situations discussed during Phase 1 about taking prescription medication. Results: Three main themes emerged from the findings: knowledge about prescription medication, barriers to taking prescription medication, and facilitators to taking prescription medication. Conclusions: The findings of the study will help to inform healthcare professionals on how to better support adults with intellectual disabilities to take their prescription medication to ensure better health outcomes.