Background Head injury is a common reason children present to EDs. Guideline development to improve care for paediatric head injuries should target the information needs of ED clinicians and factors influencing its uptake. Methods We conducted semi-structured qualitative interviews (November 2017-November 2018) with a stratified purposive sample of ED clinicians from across Australia and New Zealand. We identified clinician information needs, used the Theoretical Domains Framework (TDF) to explore factors influencing the use of head CT and clinical decision rules/guidelines in CT decision-making, and explored ways to improve guideline uptake. Two researchers coded the interview transcripts using thematic content analysis. Results A total of 43 clinicians (28 doctors, 15 nurses), from 19 hospitals (5 tertiary, 8 suburban, 6 regional/rural) were interviewed. Clinicians sought guidance for scenarios including ED management of infants, children with underlying medical issues, delayed or representations and potential non-accidental injuries. Improvements to the quality and content of discharge communication and parental discussion materials were suggested. Known risks of radiation from head CTs has led to a culture of observation over use of CT in Australasia (TDF domain: beliefs about consequences). Formal and informal policies have resulted in senior clinicians making most head CT decisions in children (TDF domain: behavioural regulation). Senior clinicians consider their gestalt to be more accurate and outperform existing guidance (TDF domain: beliefs about capabilities), although they perceive guidelines as useful for training and supporting junior staff. Summaries, flow charts, publication in ED-specific journals and scripted training materials were suggestions to improve uptake. Conclusion Information needs of ED clinicians, factors influencing use of head CT in children with head injuries and the role of guidelines were identified. These findings informed the scope and implementation strategies for an Australasian guideline for mild-to-moderate head injuries in children.