Introduction: In understanding of the general public’s knowledge, attitude and practice (KAP) on the returning and disposal of unused medications is imperative towards the designing of better educational materials and policy development. The objectives of this study was to validate the Malay version of the Return and Disposal of Unused Medications (ReDiUM) questionnaire for use among Malaysian as well as to gain an understanding on these patterns of behaviour among Malaysians. Methods: The English version of the ReDiUM was translated into Malay language according to international guidelines. Content and face validity of the questionnaire was examined by experts. Subsequently, the questionnaire was pilot tested in 10 native speakers. Reliability was assessed using Cronbach’s alpha coefficients. The test-retest reliability was measured with Spearman’s Correlation Coefficient and Cohen’s κ coefficient. Public were recruited through convenient sampling for the study. Results: The study recruited 319 respondents. For test-retest reliability, all the correlation coefficient values were >0.5 indicating strong reliability (26 respondents). Except few items, most of the kappa coefficients were >0.61 indicating substantial to almost perfect agreement. Cronbach’s alpha of the KAP domains were 0.585, 0.770 and 0.759, respectively. The median knowledge score was only 50% with some negative attitudes and practices found. Conclusions: The translated questionnaire was valid and reliable for use in Malaysia with acceptable to strong internal consistency and most items with substantial to almost perfect agreement. The findings from the study provide supporting evidence for policy makers to develop interventions to help with reducing wastage and optimize healthcare expenditure.