This two-year longitudinal study examined the role of linguistic interdependence between Spanish and English among a group of first, second, and third generation immigrant Spanish-English bilingual children. Starting from a theoretical perspective on linguistic interdependence that takes into account linguistic constructs and their measurement, the study reports on the English developmental trajectories of 112 Latinx bilinguals in second, third, and fourth grade. Multilevel growth modeling was used to develop trajectories for English vocabulary, morphology, syntax, and semantics and assess the degree to which they were predicted by initial levels of Spanish vocabulary and Spanish syntax. Findings showed that Spanish syntax was a significant predictor for English intercepts for both syntax and morphology. These cross-linguistic effects were moderated by generation status such that the effect of Spanish syntax on English morphology and syntax was, in fact, negative for first-generation students, while positive for second and third generation students. The finding that more metalinguistically focused constructs (syntax and morphology) are robust to cross-linguistic association is consistent with current theories on linguistic interdependence. Because the groups were comparable on Spanish syntax performance, the effect of generation status has some implications for levels of English proficiency necessary in order for linguistic interdependence to manifest.