The brain is highly vulnerable to neurotoxic agents during the prime learning period of a child's life. Paediatric patients with brain tumours who are treated with cranial radiation therapy (CRT) often go on to develop neurocognitive deficits, which are reflected in poor academic achievement and impaired memory, attention and processing speed. The extent of these delayed effects varies with radiation dose, brain volume irradiated, and age at treatment, and might also be influenced by genetic factors and individual susceptibility. CRT-induced impairment involves axonal damage and disruption of white matter growth, and can affect brain structures implicated in memory function and neurogenesis, such as the hippocampus. In this article, we review the underlying mechanisms and clinical consequences of CRT-induced neurocognitive damage in survivors of paediatric brain tumours. We discuss the recent application of neuroimaging technologies to identify white matter injury following CRT, and highlight new radiation techniques, pharmacological and neurological interventions, as well as rehabilitation programmes that have potential to minimize neurocognitive impairment following CRT.