Introduction Mass gathering events can lead to an increased incidence of injury and/or illness for attendees, compared to expected rates in the host community. Health interventions provided by in-event health services at mass gathering events can reduce the demand on local health system. This paper aims to identify the in-event health interventions used by health providers at mass gathering events. Methods This scoping review was guided by the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews checklist and explanation. Analysis focused on mass gathering events that had an in-event health service providing at least one health intervention. Interventions were deductively coded against the surge capacity domains of staff, stuff/supplies, space, and systems. Results A total of 41 papers were included in this review. The median patient presentation rate was 6.2/1000 attendees. The median transport to hospital rate was 0.35/1000. The most frequently reported interventions against the four ‘S’ surge capacity domains included: medications (n = 23/41, 56.1 %), procedural interventions (n = 23/41, 56.1 %) in stuff/supplies; presence of medical doctors (n = 34/41, 82.9 %) in staff; health support (n = 18/41, 43.9 %) in systems; and mobile (n = 23/41, 56.1 %) or temporary structures (n = 21/41, 51.2 %) in spaces. Conclusion This review provides an overview of possible health interventions that in-event health service providers can utilise. The health interventions provided by in-event health service at mass gathering events should be considered as one part of a broader health approach. Future research evaluation should include a cost of health interventions and their benefits to health systems.