This study explores influences on bilingual children's phonological awareness (PA) performance in English, examining the role of language of instruction and vocabulary. English monolingual and Spanish-English bilingual kindergartners and first graders receiving either English or Spanish literacy instruction were assessed in English PA and in English and Spanish vocabulary, as appropriate. Spanish-instructed bilinguals were more likely than English-instructed bilinguals or English monolinguals to treat diphthongs as two units, reflecting their analysis in Spanish phonology and orthography. Surprisingly, unbalanced bilinguals dominant in either English or Spanish scored better on English PA than children with approximately equal scores on the English and the Spanish vocabulary test. This finding suggests that familiarity with many lexical items within a language constitutes a source of analyzable phonological knowledge.