Because of the growing participation of mothers in the labour market, a large number of children have been enrolled in childcare. In the last few years, an important literature has analysed the role of childcare in child development. The aim of this chapter is to explore the impact of childcare on child outcomes and its disparities, using the Millennium Cohort Survey (MCS) for the United Kingdom, which provides very detailed information on childcare and child outcomes. We first explore the association between formal childcare and child cognitive outcomes, allowing the effect of formal childcare to be different for children from different family backgrounds. Second, we simulate how an increase in formal childcare use can affect inequalities across children. Our results report that there is a significant association between childcare attendance and several child cognitive outcomes and that an increase in childcare attendance contributes to reduce inequalities across children.