ObjectiveType 2 diabetes is a leading contributor to the burden of disease in South Africa. Primary care is struggling to support self-management and lifestyle change. Group empowerment and training (GREAT) for diabetes is a feasible and cost-effective intervention in our setting. This study aimed to evaluate the implementation of GREAT for diabetes.DesignA convergent mixed-methods study evaluated a range of implementation outcomes: acceptability, appropriateness, adoption, feasibility, fidelity, reach and cost.SettingTen primary care facilities from a district in all nine provinces of South Africa.ParticipantsDescriptive exploratory individual semistructured interviews were conducted with 34 key stakeholders from national policy-makers to primary care providers. Three focus group interviews were held with 35 patients.ResultsThe National Department of Health saw GREAT as an acceptable and appropriate intervention, but only five of the nine provinces adopted GREAT. District-level and facility-level managers also saw GREAT as an acceptable and appropriate intervention. Factors related to feasibility included physical space, sufficient staff numbers, availability of resource materials, the health information system, adaptation to the model of care (selection of facilities, patients, adjustment of patient flow and appointment systems, leadership from local managers and the whole clinical team) and inclusion in systems for quality improvement. No major changes were made to the design of GREAT and fidelity to the session content ranged from 66% to 94%. Incremental costs were US$494 per facility. Due to disruption from the COVID-19 pandemic, only 14 facilities implemented and reached 588 patients at the time of evaluation.ConclusionKey lessons were learnt on how to implement GREAT for diabetes in a middle-income country setting. The findings informed the design of a programme theory using a health system framework. The programme theory will guide further scale-up in each province and scale-out to provinces that have not yet implemented.QuestionThis study focused on evaluating how to implement GREAT for type 2 diabetes in primary care and to take it to scale in South Africa.FindingThe findings led to a programme theory on how to successfully implement GREAT for diabetes in the South African context.MeaningThe study demonstrates relevant contextual factors that need to be considered in the implementation of group diabetes education programme in a middle-income country.