The Mayo-Portland Adaptability Inventory (MPAI; designed to be administered by clinicians) is a popular measure of disability following head injury in adults. Its acceptability, validity, and reliability were assessed for use with children. There were 335 children and adolescents (215 males, 120 females) aged between 1 and 19 years at injury (median age 9y 8mo [SD 5y]) in our sample. The test was acceptable to respondents, rapidly and easily administered, and required only small modifications. It demonstrated validity against client and parent reports of major symptoms. It demonstrated test–retest reliability within the limitations of our data and excellent interrater accord. Consequently, the MPAI is recommended for paediatric use for evaluating rehabilitation needs and therapy outcome.