In this paper we examine whether – conditional on other family inputs – bilingual children achieve different outcomes in language and emotional development. Our data come from the UK Millennium Cohort Study (MCS) which allows us to analyze children's language and emotional development in depth. We relax the usual assumption that the production function underpinning child development is not itself a function of the age of the child and estimate the bilingual gap in children's language and emotional development as a cumulative process that depends on current and past endowments of cognitive and non-cognitive capacity. We find that the language development of bilingual children is not significantly different to that of their monolingual peers; however, there is evidence of a positive effect of bilingualism on emotional development.