The study purposes to explore the effects of individual characteristics and home environments of children on their bilingual language aquisition, that is, to examine whether their English language competency is different from their Korean language competency depending on those variables. Thus English or Korean language competency of children who had had early exposure in English learning were studied in terms of child's individual characteristics such as age, gender, exposure period to English, intelligence, and experiences of visiting English-speaking countries, and home environments such as parental age, educational level, income level, their perceived English competency, their perceived significance of English and Korean language, and the frequency of using English at home. 72 children who went to English kindergarten were tested with Peabody Pictures Vocabulary Test-Revised (PPVT-R) in Korean version and in English version respectively. The results show that child's intelligence and experiences of visiting English-speaking countries influence their Korean language competency. Also child's age, exposure period to English and experiences of visiting English-speaking countries influence their English language competency. Moreover their mother's educational background, father's English fluency, mothers' English fluency, and the frequency of using English at home influence child's English language competency, whereas any variables did not influence child's Korean language competency. Accordingly, child's English and Korean language competencies are related to each other.