The aim of this study was to examine whether individual, family and peer factors can increase the risk of polysubstance use in Taiwanese adolescent ecstasy users. Two hundred adolescents with ecstasy use were recruited into this study. Their experience of using any other harmful substance in the preceding year and a variety of individual, family and peer characteristics were collected. The correlates of polysubstance use were examined using the two-step procedure of variable selection. The results indicated that 59 (29.5%) of the adolescent ecstasy users were polysubstance users. Ketamine, alcohol and areca quid were the three most prevalent substances used. Users who experienced dropping out of school, had poor mental health status and whose fathers had a low education level had an increased risk of polysubstance use. Clinicians should thoroughly screen adolescent ecstasy users who have the above factors as they are more likely to use other substances concomitantly.