Background Little is known about the successful experiences and positive perceptions of people with intellectual disabilities (ID) self-managing Type 2 Diabetes (T2D). This study sought to address this gap using Bandura's (1977) ‘Four Sources of Self-Efficacy’ as a framework of enquiry. Method Semi-structured interviews were conducted with 10 adults with ID. Interviews were recorded, transcribed verbatim and analysed using inductive and deductive thematic analysis Results Nine sub-themes were identified following analysis of the data: 1) Mastery through knowledge; 2) Mastery through tools and strategies; 3) Mastery through autonomy; 4) Influence of social setting; 5) Positive social comparisons; 6) Positive and negative self-statements; 7) Feedback from caregivers; 8) Adjustment experiences; 9) Symptom awareness. These were mapped onto Bandura's (1977) Four Sources of efficacy enhancement model and were consistent with its proposed mechanisms. Conclusion The Four Sources model serves as a useful mode of enquiry for exploring people with ID's experiences and perceptions of self-managing diabetes. It also confirms the appropriateness of Self-efficacy as a potential intervention component for this population. However, additional support may be required for people with ID to reflect meaningfully on their experiences and thus have a sense of self-efficacy. What this paper adds This paper builds upon the limited existing literature on people with ID self-managing type 2 diabetes and provides a robust, qualitative account of the participants' experiences, whilst confirming some of the existing challenges, both for people with ID and their supporters. To self-manage with autonomy and overcome the difficulties of adjustment, further strategies such as training and education needs are highlighted. In addition, the meaning and relevance of the Self-efficacy construct is evaluated in the context of people with ID self-managing T2D. This provides useful information in terms of tailoring existing mainstream T2D interventions to meet the needs of people with ID, as such programs are commonly theoretically guided by Self-efficacy. Furthermore, this evaluation provides rationale for the exploration of people with IDs’ Self-efficacy in relation to other chronic diseases, such as cardiovascular disease, cancer symptoms and gastrointestinal disorders.