Background: Childhood externalizing and internalizing behaviors have been associated with injury risk in childhood and adolescence, but it is unknown whether this association continues to hold in adulthood. We examined whether externalizing and internalizing behaviors expressed in childhood predict injuries in childhood, adolescence, and adulthood. Methods: The participants were from the 1958 British birth cohort (n = 11,537). Problem behaviors were assessed by teachers at ages 7 and 11. Injuries were reported by the participants' parents (at ages 7, 11, 16) and by the participants (at ages 23, 33, 42, and 46). Data on injury severity were available at ages 23 and 33, and on types of injuries at ages 23, 33, and 42. Measures of childhood family environment included father's social class, family size, and family difficulties. Adult psychological distress, treated as a potential mediating factor, was assessed at ages 23, 33, and 42. Results: Externalizing behavior predicted increased injury risk: one SD increase in externalizing score was associated with 10-19% increase in the rate of injuries in childhood, adolescence, and adulthood. In contrast, internalizing behavior decreased injury rate by 3-9% in adolescence and adulthood. Externalizing behavior was associated with various types of injuries, including injuries in traffic, at home, at work, and from violent assaults, while internalizing behavior predicted decreased injury risk particularly in sports, in traffic, and at home. These associations were largely independent of childhood family environment and adult psychological distress. Conclusions: The findings suggest that childhood problem behaviors predict injury risk over the life course from childhood to midlife, with externalizing behaviors increasing and internalizing behaviors decreasing this risk.