Drawing on the National Educational Longitudinal Survey 1988 (NELS:88), this study identified (1) the growth pattern of academic achievement of adolescent children from Mexican and East Asian immigrant families; (2) investigated to what extent ethnicity and family capital influenced the trajectories in the academic achievement of children from Mexican and East Asian immigrant families in the United States. The growth curve model analysis showed that ethnicity had a significant main effect on academic trajectories. Taking into account various forms of family capital, however, there was no significant ethnicity effect on the rate of change. In addition, compared to parents with a lower level of family capital, those whose families had higher levels of capital generally did better at eighth grade and these students' achievement accelerated over time. Implications and limitations are also discussed.