Background: The effects of child care services on several domains of child development have been extensively investigated, but evidence regarding the effects of child care on language development remains inconclusive. Methods: Within a large-scale population-based study, we examined the longitudinal associations between non-parental child care and language development from 1 to 6 years (n = 5375). Results: Results showed that more hours in non-parental child care were associated with better language abilities. However, more hours in care in the first year of life were associated with less language proficiency at ages 1 to 1.5. At later ages, this effect disappeared and language proficiency increased. Furthermore, children who spent more hours in centre-based care had better language scores than children in home-based care. Ethnicity, socio-economic status, gender or parity did not change these results. Conclusions: This large, multi-ethnic study demonstrates beneficial effects of non-parental child care, particularly centre-based care, on language proficiency later in childhood.