Introduction: Older (age >=65 years) trauma patients suffer increased morbidity and mortality. This is due to under-triage of older trauma victims, resulting in lack of transfer to a trauma centre or failure to activate the trauma team. There are currently no Canadian guidelines for the management of older trauma patients. The objective of this study was to identify modifiers to the prehospital and emergency department (ED) phases of major trauma care for older adults based on expert consensus. Methods: We conducted a modified Delphi study to assess senior-friendly major trauma care modifiers based on national expert consensus. The panel consisted of 24 trauma care providers across Canada, including medical directors, paramedics, emergency physicians, emergency nurses, trauma surgeons and trauma administrators. Following a literature review, we developed an online Delphi survey consisting of 16 trauma care modifiers. Three online survey rounds were distributed and panelists were asked to score items on a 9-point Likert scale. The following predetermined thresholds were used: appropriate (median score 7–9, without disagreement); inappropriate (median score 1–3; without disagreement), and uncertain (any median score with disagreement). The disagreement index (DI) is a method for measuring consensus within groups. Agreement was defined a priori as a DI score <1. Results: There was a 100% response rate for all survey rounds. Three new trauma care modifiers were suggested by panelists. Of 19 trauma care modifiers, the expert panel achieved consensus agreement for 17 items. The prehospital modifier with the strongest agreement to transfer to a trauma centre was a respiratory rate <10 or >20 breaths/minute or needing ventilatory support (DI = 0.24). The ED modifier with the strongest level of agreement was obtaining a 12-lead electrocardiogram following the primary and secondary survey for all older adults (DI = 0.01). Two trauma care modifiers failed to reach consensus agreement: transporting older patients with ground level falls to a trauma centre and activating the trauma team based solely on an age >=65 years. Conclusion: Using a modified Delphi process, an expert panel agreed upon 17 trauma care modifiers for older adults in the prehospital and ED phases of care. These modifiers may improve the delivery of senior-friendly trauma care and should be considered when developing local and national trauma guidelines.