OBJECTIVES: To translate the MMAS into the Malaysian language, and to examine the psychometric properties of the Malaysian version of the MMAS among patients with type 2 diabetes, including its validity and reliability. METHODS: After obtaining permission, a standard “forward-backward” translation procedure was used to create the Malaysian version of the MMAS from the original English version. A convenience sample of 223 outpatients with type 2 diabetes was identified between May and September, 2009. All data were collected from the Penang General Hospital, Penang, Malaysia. Instruments consisted of the Malaysian version of MMAS, the Malaysian version of the old four-item Morisky scale and a sociodemographic questionnaire. Medical records were reviewed for haemoglobin A1C (HbA1C) levels and other clinical data. Reliability was tested for internal consistency using Cronbach’s α coefficient. Validity was confirmed using convergent and known group validity. RESULTS: Employing the recommended scoring method, the mean ± SD of MMAS scores was 6.13 ± 1.72. Moderate internal consistency was found, (Cronbach’s α = 0.675), the test-retest reliability value by using Spearman's rank correlation was 0.816 (p<0.001). A positive correlation between the eight- and four-item MMAS was found (r= 0.792; p<0.01). For known group validity, a significant relationship between MMAS categories and HbA1c categories (χ2= 20.261; p≥0.001) was found. The MMAS sensitivity and specificity, with positive and negative predictive values were 77.61%, 45.37%, 46.84% and 76.56%, respectively.  CONCLUSIONS: : The MMAS can be used for medication adherence measurement in diabetes. The findings of this validation study indicate that the Malaysian version of the MMAS is a reliable and valid measure of medication adherence which can now be used in clinical practice.