Understanding the mechanisms underlying the development of migrants' second language (L2) competence in naturalistic settings is a pressing concern for receiving societies. Several studies have established a positive relation between people's self-positioning with respect to the L2 ethnolinguistic group and their L2 competence, but the mechanisms underlying this relation are relatively unexplored. Using path analysis, this study investigates the hypothesis that migrants' experience with the L2 mediates the positive association between mainstream cultural orientation and self-assessed L2 competence among 123 multicultural recent immigrant students to Montreal, Quebec. As such, this study applies notions from L2 motivation and sociocultural L2 learning to an acculturation context. This study also unpacks L2 experience by examining L2 use and L2 social contact (namely, friendships in the mainstream group) separately. In addition, this study takes into account the important role of the social context by selecting a setting that maximizes the centrality of individual differences in cultural orientations. The hypotheses were fully supported: model fit for the hypothesized model was excellent and better than for alternative models.