Paediatric acquired brain injury (ABI) is the most common cause of acquired disability in childhood. It frequently results in significant personality, cognitive, emotional and behavioural changes, and consequent impairment in independent functioning, education, employment and interpersonal relationships. Additionally, paediatric ABI impacts on the entire family system, with parents commonly reporting significant distress and adjustment difficulties. Despite this, there is currently limited research into effective programmes to support families following their child's ABI. This protocol describes a wait-list randomised controlled trial of a behavioural family intervention plus a parent stress management programme for paediatric ABI. Interventions will be conducted with parents in a group format, aiming to improve child outcomes by improving parenting behaviour and coping. Outcomes assessed will be: (i) child behaviour and emotional outcome as measured by parent and teacher reports; (ii) parental style and confidence; (iii) parental adjustment (stress, anxiety and depression symptoms); (iv) family functioning; (v) parent relationship; and (vi) parent psychological flexibility. Assessments will be via questionnaires conducted pre-, mid- and post- intervention, and at a 6-month follow-up. The theoretical basis, study hypotheses, methods and planned analyses are described.