We designed a longitudinal retrospective cohort study to analyse the associations between neighbourhood social capital and child injures. Register data from the Umeå Simsam Lab in Sweden was used to measure child injuries and demographic and socioeconomic factors at individual, household and neighbourhood level. A social capital score from a previous survey was used to measure neighbourhood social capital. We conducted a three-level multilevel negative binomial regression analysis, with children (level 1, N = 77,193) nested within households (level 2, N = 10,465), and households nested within neighbourhoods (level 3, N = 49). The incidence rate of child injuries was lower in high social capital neighbourhoods. When controlling for factors at individual, household and neighbourhood levels, living in a high social capital neighbourhood was protective of injuries among girls, but not among boys. Promoting social capital in local neighbourhoods could be seen as a prevention strategy for injuries among girls.