This paper takes a sociocultural approach to exploring the factors that enhance young children's bilingual development. The language excerpts presented were gathered as part of a three-year Early Childhood Centre of Innovation project funded by the New Zealand government. Data gathered in this project challenge Krashen's (1981) position that young children will generally acquire another language through subconscious osmosis, rather than through the conscious effort of learning. Evidence is put forward that illustrates how young children's bilingual development is in fact mediated by their teachers and peers, as well as the cultural tools provided in the environment and the nature of the language input itself. Young children are also revealed as active language learners who interact collaboratively with others and with their environment. Thus, the value of early childhood teachers in taking a more proactive role to support the process of young children's bilingual development is affirmed.