ABSTRACT This longitudinal study examined the latent structure of self-concept and its association with academic performance for elementary-aged students enrolled in dual-language immersion (DLI) and English-medium instruction (EMI) programs. Participants were 30 students in a Spanish-English DLI program and 40 peers in the same school’s EMI classrooms. The present study used confirmatory factor analysis to examine the structure of self-concept and multilevel growth modeling to investigate the effect of self-concept on academic performance tested in English. Results confirmed a three-factor self-concept construct and differences in several factors by program enrollment. Gender moderated the association between different factors of self-concept and academic performance. These findings suggest important educational implications: more attention to students’ early self-concept may be required as it plays a prominent role in students’ on-going academic achievement.