In this empirical analysis, we estimate the link between formal childcare and child cognitive outcomes, controlling for a large number of variables. We use the Millennium Cohort Survey (MCS) for the United Kingdom, which provides very detailed information about several modalities of childcare as well as several child outcomes. We also simulate how an increase in formal childcare attendance can affect inequalities across children. Our results indicate that childcare attendance has a positive impact on child cognitive outcomes, which are stronger for children from low socioeconomic background.