The aim of this study was to examine the effect of brief modified motivational enhancement therapy (MET) on readiness to change patterns of methylenedioxymethamphetamine (MDMA) and methamphetamine (MAMP) use behaviors in adolescents. A total of 94 adolescents who used MDMA or MAMP were consecutively recruited from a juvenile abstinence center; 46 received a three-session MET intervention (intervention group), and 48 received educational materials only and no MET intervention (control group). Analysis of covariance was performed to examine the effect of motivational interviewing on the readiness of change scores on the University of Rhode Island Change Assessment and on the scores of its subscales. By using the pretreatment scores as covariates, the intervention group demonstrated higher posttreatment scores of readiness to change and of the contemplation subscale on the University of Rhode Island Change Assessment than the control group. The results of this study support the finding that brief modified MET is effective in promoting readiness to change MAMP and MDMA use behaviors in adolescents who receive short-term treatment programs.