Research examined the influence of native vocabulary development on cross-language transfer of phonemic awareness. Participants were Spanish-speaking kindergartners learning English in immersion classrooms. Results indicated that limited Spanish vocabulary development negatively influenced cross-language transfer of phonemic awareness to English. The results have clear and profound implications for Spanish-speaking children. Without foundational Spanish vocabulary skills needed to facilitate cross-language transfer of phonemic awareness to English, literacy acquisition difficulties will likely arise. (Contains 8 tables.)