OBJECTIVES: Diabetes mellitus is a serious health problem. Medication adherence is a key determinant of therapeutic success in patients with diabetes mellitus. The purpose of this study was to assess medication adherence and its potential association with diabetes related knowledge in patients with type 2 diabetes mellitus.  METHODS: This study was carried out at the outpatient clinics of a public sector teaching hospital in Sargodha, Pakistan. Besides demographic and disease-related questions, previously validated questionnaires, Morisky Medication Adherence Scale and Michigan diabetes knowledge test was used to assess the medication adherence and diabetes related knowledge, respectively. Descriptive statistics were used to determine the demographic and disease characteristics of the patients while Spearman rank correlation was employed to measure the association between medication adherence and knowledge.  RESULTS: Three hundred and ninety two patients were interviewed. Out of 392 patients, 245 (62.5%) of the patients had average knowledge about diabetes while 282 (71.9 %) were categorized as poor adherent. Only 13 patients (3.3 %) were considered as good adherent in the study. The correlation coefficient between total scores of knowledge and total medication adherence score was 0.036 (p< 0.05), indicating a weak correlation between knowledge scores and adherence level. CONCLUSIONS: Knowledge of diabetes mellitus among these patients was average; however, adherence to drug therapy was also poor. Patients’ knowledge about diabetes had positive association with medication adherence. Improving diabetes knowledge of people can result in better adherence, which may result in better control of diabetes.