The purpose of this study is to examine the influence of youth activities on bicultural attitude and the mediating effect of peer relationship. To verify research hypotheses, using data from the 9th wave of the 1st Multicultural Adolescents Panel Study(MAPS), direct and indirect effects were analyzed with the PROCESS Macro’s Model 4. The main findings are as follows. First, multicultural adolescents’ participation in activities positively and significantly influenced bicultural attitude. Second, a partial mediating effect of multicultural adolescents’ peer relationship was found on the influence of youth activities on bicultural attitude. That is, the level of participation in youth activities increased the level of peer relationship, which in turn increased the level of bicultural attitude. Based on the above-mentioned main findings, this study suggests strategies to promote multicultural adolescents’ bicultural attitude through youth activities.