A prospective study was conducted to evaluate medication adherence behavior in HIV/AIDS patients on antiretroviral therapy. Brief Medication Questionnaire (BMQ), a screening tool to assess medication adherence behavior and barriers to adherence was administered on study population at base line and final follow up of the study period. The study population received education regarding their disease, medications and importance of adherence to medication at each follow-up. The study patients with negative BMQ screen scores were considered as adherent to the antiretroviral medications. Influence of patient education was assessed by comparing the pre and post educational BMQ scores. Higher mean regimen, belief, recall, and medication access screen scores at the baseline suggested the non-adherent behavior of the study population. At final follow up, a significant decrease (p<0.01) in the regimen, belief, access and total screen scores of BMQ suggested the improvement in adherence behavior. Our study also observed a significant increase (p<0.01) in the number of patients, shifting from positive screen to negative screen scores of BMQ. The results of our study suggested the need for continuous patient education in HIV/AIDS patients to improve the adherence behavior and effectiveness of their medications to achieve desired therapeutic out comes. Pharmacist provided education sessions were found to be effective in improving medication adherence behavior of HIV/AIDS patients.