Diabetes mellitus (DM) is a complex chronic condition and remains a public health concern worldwide. In South Africa (SA), many patients with DM access public sector primary healthcare clinics, and those who are considered to be stable are referred to the club system, which is managed by a multidisciplinary team. Patients who have DM are often diagnosed with concurrent medical conditions, resulting in multiple medication therapies that lead to medication therapy problems (MTPs). Prescriber adherence to standard treatment guidelines (STGs) is aimed at improving glycaemic control to minimise complications and decrease healthcare costs. The pharmacist's role in medication therapy management (MTM) for DM is underutilised in public sector healthcare facilities. Objectives. To evaluate the implementation of a pharmacist-led MTM intervention to optimise the management of stable patients with type 2 DM attending a diabetes club at a Cape Town community day centre. Methods. An evaluation study design using a case study approach was conducted over 8 months from November 2016 to June 2017. A retrospective and prospective audit was conducted from patient folders of stable patients who attended the club. Quantitative data were extracted from the folders. A trained pharmacist audited baseline (pre-intervention) data. Prescribing staff were notified of therapeutic discrepancies through written pharmacist's pharmacotherapeutic recommendations (intervention). Pharmacist-led interventions audited prescriber adherence to SA STGs and the Essential Medicines List, and prescriber responses to the pharmacist's recommendations (post-intervention) were recorded as accepted, partially accepted or rejected. Estimated costs were calculated for rational and irrational prescribing of aspirin during the MTM process. Results. Of 104 patient folders audited, most were for females (n=70; 67.3%). A total of 453 MTPs were identified, averaging four interventions per folder reviewed. The most common MTPs identified were the absence of basic clinical data: body mass index not documented (22.5%) in the folder, no medical indication noted (19.2%), and laboratory tests not requested (18.3%) by clinicians. Prescriber acceptance of the pharmacist's recommendations was found to be low (26.8%), suggestive of clinical inertia. Aspirin was found to be irrationally prescribed to patients with DM (15.4%). Conclusion. Pharmacists can identify, resolve and prevent MTPs and rationalise appropriate medication therapy in patients with DM. Prescriber uptake of pharmacists' pharmacotherapeutic recommendations seems overlooked. Pharmacist-led workshops to advocate for rational prescribing are needed to mitigate MTPs among stable patients with type 2 DM at public sector healthcare facilities.