OBJECTIVE To validate the Diabetes Medication Adherence Scale (DMAS-7), determine its concordance with another validated scales and to assess factors affecting medication adherence. METHODS A cross-sectional study was conducted on a sample of Lebanese patients with diabetes using a questionnaire. The level of adherence was measured using the DMAS-7 and the Lebanese Medication Adherence Scale (LMAS-14). Bivariate and multivariate analyses were conducted, and the scale was validated in terms of reliability, predictive ability, and construct validity using SPSS version 19. RESULTS Out of 300 eligible patients, the rate of adherence was 33.7%. Measures of validity showed good reliability (Cronbach alpha = 0.627), and good construct validity with LMAS-14 (Spearman's rho = 0.846; Cohen's kappa = 0.711). DMAS-7 was found to be both correlated with LMAS-14 (ICC average measure = 0.675; p-value <0.001) in addition to possessing a better predictive value. Thus, DMAS-7 showed to have good concordance and increased validity compared to LMAS-14. Having an optimal glycated hemoglobin (HbA1C) (OR = 0.779; p = 0.001) and performing regular physical activity (OR 2.328; p = 0.002) increased medication adherence. CONCLUSIONS The DMAS-7 showed to be reliable and valid instrument superior to LMAS-14 in predicting adherence levels to oral anti-diabetic medications, and thus can be used to achieve better glycemic outcomes.