The authors investigated the influence of language proficiency on the cross-language transfer (CLT) of phonemic awareness in Spanish-speaking kindergarten students and assessed Spanish and English receptive vocabulary and phonemic awareness abilities. Correlation results indicated positive correlations between phonemic awareness across languages; CLT occurred. To investigate the role of proficiency in native language (L1) in CLT, the authors disaggregated the sample into two groups by L1 receptive vocabulary. No evidence for CLT of phonemic awareness emerged among children with below-average L1 skills. Regression results indicated that L1 receptive vocabulary predicted phonemic awareness performance of children's language of instruction. The authors suggest that prereading skills may transfer from L1 to L2 following a different pattern in children lacking L1 proficiency. Further investigation of CLT among children with below-average L1 skills is needed. (Contains 7 tables.)