BACKGROUND Accidental injury represents the most common type of traumatic event experienced by children under the age of 6 years. Around 10-30 % of young injured children will go on to develop post-traumatic stress disorder (PTSD) and other co-morbid conditions. Parents of injured children are also at risk of PTSD, and this is associated with short- and long-term consequences for their children's physical and psychological recovery. Despite the significance of this problem, to date, the mental health needs of injured young children have been neglected. One reason for this is due to the uncertainty and considerable debate around how to best provide early psychological intervention to traumatised children and adults. To address these gaps, researchers and psychologists in Australia and Switzerland have developed the Coping with Accident Reactions (CARE) programme, which is a two-session early intervention designed to prevent persistent PTSD reactions in young injured children screened as 'at risk'. Two separate international studies are being conducted to evaluate the effectiveness and feasibility of this programme. METHODS/DESIGN The study design for the two proposed studies will employ a randomised controlled trial design and children (aged 1-6 years) who are screened as at risk for PTSD 1 week after an unintentional injury, and their parents will be randomised to either (1) CARE intervention or (2) treatment as usual. Assessment will be completed at baseline (2 weeks) and 3 and 6 months post-injury. DISCUSSION This international collaboration provides an excellent opportunity to test the benefit of screening and providing early intervention to young children in two different countries and settings. It is expected that outcomes from this research will lead to significant original contributions to the scientific evidence base and clinical treatment and recovery of very young injured children. TRIAL REGISTRATION The Australian study was registered with the Australian New Zealand Clinical Trials Registry ( ACTRN12614000325606 ) on 26 March 2014. The Swiss study was registered with ClinicalTrials.gov ( NCT02088814 ) on 12 March 2014.