Adherence with multidrug therapy (MDT) is one of the keys to successful treatment of leprosy. In order to understand the treatment behavior, reasons for non-adherence, and efforts to improve medication adherence, it is necessary to use a valid and reliable instrument to measure adherence to MDT in multibacillary leprosy patients on regular basis. This study used a mixed method de-sign. The instrument development phase involved 10 experts using 4 rounds of Delphi method. Assessment items that are considered relevant are those that meet 4-5 Likert scale by a minimum of 75% of experts or meet assessment score >3.75. We did the pilot testing and the questionnaire was revised if invalid. After obtaining a valid and reliable instrument, it was tested to 100 sub-jects in 4 health centers. For internal validity test, 9 valid assessment items were obtained, with the correlation coefficient values of each item >0.3, and -Cronbach's reliability of 0.723. The instru-ment produced had sensitivity of 88.46% and specificity of 78.37%. From 100 subjects enrolled, 61% had good adherence and 39% had poor adherence based on questionnaire assessment. A valid and reliable questionnaire for evaluating adherence with MDT in Indonesian patients has been composed.