A critical issue facing the majority of immigrant adolescents in U.S. public schools is persistent academic underperformance. Using data from the Children of Immigrants Longitudinal Study, this study investigates the extent to which negative social environments in U.S. public schools predict the academic achievement of immigrant adolescents. Importantly, we simultaneously examine the roles of both the relational (individual-level) and structural (school-level) characteristics of these negative social environments. Multilevel structural equation modeling revealed that immigrant students who are embedded in more negative relationships (e.g., having peers who discriminate against them) have lower levels of academic achievement. These predictive effects of individual-level negative social environments on academic achievement are mediated by both perceived school safety and educational expectations. Furthermore, we find double mediation effects (i.e., three-pathway mediations) via perceptions of school safety and educational expectations. The existence of these double mediation effects implies that relational characteristics strongly predict immigrant adolescents' perceptions, attitudes, and school outcomes. Finally, we find that structural characteristics of negative social environments in U.S. public schools (i.e., total student enrollment and school-level dropout rate) also negatively predict immigrant adolescent achievement. We discuss the implications of these findings for improving immigrant adolescents' achievements in U.S. public schools.