Purpose: sequential bilingual children in the united states often speak 2 languages that have different social statuses (minoritymajority) and separate contexts for learning (home school). Thus, distinct factors may support the development of each language. This study examined which child internal and external factors were related to vocabulary skills in a minority language versus english. Method: participants included 69 children, aged 58 years, who lived in southern california, spoke vietnamese as the home language, and received school instruction in english. All participants had at least 1 foreign-born parent, and most mothers reported limited english proficiency. Parents completed a telephone survey, and children completed measures of receptive and expressive vocabulary in each language. Using correlations and stepwise regression, we examined predictors of vocabulary skills in each language that were internal to the child (age, gender, analytical reasoning, phonological memory) or that pertained to the surrounding environment (cumulative exposure, quantity and quality of input/output). Results: vietnamese vocabulary outcomes were related to multiple external factors, of which input and enrichment activities were the best predictors. In contrast, english vocabulary outcomes were related to internal factors, of which age and phonological memory were the best predictors. Parental use of vietnamese contributed to childrens vietnamesevocabularyoutcomesbutwasnot related to childrens english vocabulary outcomes. Conclusions: vietnamese exposure does not hinder english development. Children from immigrant families are learning english with or without familial support. Rich and frequent exposure and opportunities for practice are essential for the continued development of a minority first language. 2018 American speech-language-hearing association.