Until recently, the impact of early brain insult (EBI) has been considered to be less significant than for later brain injuries, consistent with the notion that the young brain is more flexible and able to reorganize in the context of brain insult. This study aimed to evaluate this notion by comparing cognitive and behavioural outcomes for children sustaining EBI at different times from gestation to late childhood. Children with focal brain insults were categorized according to timing of brain insult, represented by six developmental periods: (i) Congenital (n = 38): EBI: first–second trimester; (ii) Perinatal (n = 33); EBI: third trimester to 1 month post-natal; (iii) Infancy (n = 23): EBI: 2 months–2 years post-birth; (iv) Preschool (n = 19): EBI: 3–6 years; (v) Middle Childhood (n = 31): EBI: 7–9 years; and (vi) Late Childhood (n = 19): EBI: after age 10. Groups were similar with respect to injury and demographic factors. Children were assessed for intelligence, academic ability, everyday executive function and behaviour. Results showed that children with EBI were at increased risk for impairment in all domains assessed. Furthermore, children sustaining EBI before age 2 years recorded global and significant cognitive deficits, while children with later EBI performed closer to normal expectations, suggesting a linear association between age at insult and outcome. In contrast, for behaviour, children with EBI from 7 to 9 years performed worse than those with EBI from 3 to 6 years, and more like those with younger insults, suggesting that not all functions share the same pattern of vulnerability with respect to age at insult.