Background: Decision aids are patient-focused tools that have the potential to reduce the overuse of head computed tomography (CT) scans. Objective: The objective of this study was to create a consensus among Canadian mild traumatic brain injury and emergency medicine experts on modifications required to adapt two American decision aids about head CT use for adult and paediatric mild traumatic brain injury to the Canadian context. Methods: We invited 21 Canadian stakeholders and the two authors of the American decision aids to a Nominal Group Technique consensus meeting to generate suggestions for adapting the decision aids. This method encourages idea generation and sharing between team members. Each idea was discussed and then prioritised using a voting system. We collected data using videotaping, writing material and online collaborative writing tools. The modifications proposed were analysed using a qualitative thematic content analysis. Results: Twenty-one participants took part in the meeting, including researchers and clinician researchers (n = 9; 43%), patient partners (n = 3; 14%) and decision makers (n = 2; 10%). A total of 84 ideas were generated. Participants highlighted the need to clarify the purpose of the decision aids, the nature of the problem being addressed and the target population. The tools require sociocultural adaptations, better identification of their target population, better description of head CT utility, advantages and related risks, modification of the visual and written representation of the risk of brain injury and head CT use, and locally adapted, patient follow-up plans. Conclusions: This study based on a Nominal Group Technique identified several adaptations for two American decision aids about head CT use for mild traumatic brain injury to support their use in Canada’s different healthcare, social, cultural and legal context. These adaptations concerned the target users of the decision aids, the information presented, and how the benefits and risks were communicated in the decision aids. Future steps include prototyping the two adapted decision aids, conducting formative evaluations with actual emergency department patients and clinicians, and measuring the impact of the adapted tools on CT scan use.