This paper considers what early years practitioners need to know about bilingual acquisition. It argues that bilingualism is not only an asset in the classroom and the community, but also an individual and family achievement that requires commitment and determination. The different contexts of bilingual acquisition are considered, along with the implication for a successful outcome. In particular, given our current understanding of the processes of language acquisition, the role of the input in each of the two languages will be discussed; the implications of this for early years teachers/practitioners are also considered in order to find the most effective ways of supporting bilingual development in the classroom.