BACKGROUND: Children exposed to early adversity are vulnerable to cognitive impairments and externalizing behaviors. Attending childcare may, however, partly buffer this detrimental effect by providing social and cognitive stimulation in a secure environment. The aims of this study were (a) to determine whether the association between exposure to adversity and later externalizing behaviors is mediated by children's cognitive abilities, and (b) to examine if childcare attendance moderates this mediation-thereby highlighting a protective function of children's childcare attendance. METHODS: Data come from the Avon Longitudinal Study of Children and Parents (N = 6,149). Exposure to adversity was assessed by maternal reports three times from the second trimester of the mother's pregnancy to the child's fourth year of age. Childcare attendance was assessed on four occasions between eight months and three years of age. Factors explaining differences in childcare attendance were controlled using propensity score weights. Children's cognitive abilities were assessed by the Weschler Intelligence Scale for Children at eight years of age, and externalizing behaviors were reported by mothers using the Development and Well-Being Assessment interview at 10, 13, and 15 years of age. RESULTS: Notably, lower cognitive abilities partly accounted for the higher levels of externalizing behaviors in adolescents exposed to adversity (B indirect effect = 0.02, 95% CI = 0.007-0.03, p < .01). Importantly, childcare attendance moderated this indirect effect. For children exposed to adversity, being in maternal care was associated with lower cognitive abilities which were related to higher levels of externalizing behaviors. On the contrary, for children exposed to adversity, attending childcare was associated with higher cognitive abilities which were linked to lower levels of externalizing behaviors. CONCLUSIONS: Easily accessible community childcare may be a relatively low-cost public health strategy to prevent the emergence of externalizing behavioral problems in adolescence through its positive effects on cognitive abilities.< Réduire