Early development of non-cognitive skills has long-lasting benefits for children's subsequent educational attainment and wages. Drawing on a rich, nationally representative longitudinal sample of young children in Ireland, we present new evidence on whether the use of centre-based childcare (CBC) in infancy and early years promotes non-cognitive skills by school entry. We focus on the type of non-parental childcare used by mothers who are working when their child is 9 months old, comparing CBC with other forms of non-parental care. We consider the impact of childcare type on three domains of socio-emotional skills: externalizing, internalizing and prosocial behaviours. We find negative effects of CBC on both externalizing and prosocial behaviours. With a cumulative value-added model, we estimate that CBC at age 3 worsens externalizing behaviour at age 5 by 0.11 standard deviations compared to other forms of non-parental care, equivalent to 44% of the difference in externalizing behaviour between children with a mother with/without tertiary education. The effect of CBC on the externalizing dimension of socio-emotional skills of children entering school is consistent across several specifications and robustness checks. Given planned expansion of CBC for those needing subsidized provision, we conclude that such measures could exacerbate socio-emotional inequalities.This paper is part of the Economica 100 Series. Economica, the LSE "house journal" is now 100 years old. To commemorate this achievement, we are publishing 100 papers by former students, as well as current and former faculty.