Introduction: The ability to use both hands to interact with objects is required in daily activities and is therefore important to measure in clinical practice. The Assisting Hand Assessment (AHA) is unique in evaluating the function of a child or youth's assisting hand, through observing the spontaneous manipulation of objects during bimanual activity. The AHA was developed for children with unilateral motor impairment, and shows strong psychometric properties when used with children who have cerebral palsy (CP) or obstetric brachial plexus palsy (OBPP). The AHA is currently used in clinical practice with children who have an acquired brain injury (ABI), however there is limited research on the measurement properties of its use with this population. Objectives: The study aimed to determine the interrater and intrarater reliability of the AHA for children and youth with unilateral motor impairment following ABI. Methods: For interrater reliability, two occupational therapists (OT1 and OT2) independently rated the same 26 children and youth. For intrarater reliability, OT2 conducted a second assessment on the 26 participants 1 week later. Association between item scores on the AHA were analysed using weighted kappa (Kw), while intraclass correlation coefficients (ICCs) were used for domain and total scores. Results: The AHA items demonstrated good to excellent intrarater reliability (Kw = 0.67–1.00). Interrater reliability was good to excellent (Kw=0.60–0.84) for 20 of the 22 items of the AHA. Interrater and intrarater reliability coefficients for all domain and total scores were in the excellent range (ICC = 0.85–0.99). Conclusion: The current study indicates that the AHA shows good interrater and intrarater reliability when used with the paediatric ABI population. Findings provide preliminary support for the continued use of the AHA for children and youth with acquired hemiplegia.