Purpose: The present study examined the impact of environmental factors (socioeconomic status [SES], the percent of language exposure to English and to Spanish, and primary caregivers' vocabulary knowledge) on bilingual children's vocabulary skills. Method: Vocabulary skills were measured in 58 bilingual children between the ages of 5 and 7 who spoke Spanish as their native language and English as their second language. Data related to language environment in the home, specifically, the percent of language exposure to each language and SES, were obtained from primary caregiver interviews. Primary caregivers' vocabulary knowledge was measured directly using expressive and receptive vocabulary assessments in both languages. Results: Multiple regression analyses indicated that primary caregivers' vocabulary knowledge, the child's percent exposure to each language, and SES were robust predictors of children's English, but not Spanish, vocabulary skills. Conclusion: These findings indicate that in the early school ages, primary caregiver vocabulary skills have a stronger impact on bilingual children's second-language than native-language vocabulary.