To validate the International Index of Erectile Function (IIEF-15) in Malaysian population. Reliability and internal consistency were evaluated using the test-retest method and Cronbach's alpha. Sensitivity to change was expressed as the effect size index. Internal consistency was excellent (Cronbach's alpha value = 0.75 to 0.90) Test-retest correlation coefficient and intraclass correlation coefficient were highly significant (ICC = 0.75 and above) and a high degree of sensitivity and specificity was observed. The IIEF-15 is suitable, reliable, valid and sensitive to clinical change in the Malaysian population.