The current study uses an accelerated longitudinal design to examine the role of three dimensions of academic engagement (behavioral, relational, and cognitive) in explaining the influence of English language proficiency on newcomer immigrant youths' academic performance across adolescence. The sample included 354 youth from Central America, China, the Dominican Republic, Haiti, and Mexico. As established with other populations, the behavioral, relational, and cognitive dimensions of academic engagement were closely associated to one another and significantly contributed to academic performance. Mediation analyses revealed that immigrant youth with limited English language proficiency were more likely to experience low levels of relational and behavioral engagement, which contributed to lower levels of academic performance over time.