Objectives To assess the effect of a mobile phone application for prehospital notification on resuscitation and patient outcomes.Design Longitudinal prospective cohort study with preintervention and postintervention cohorts.Setting Major trauma centre in India.Participants Injured patients being transported by ambulance and allocated to red (highest) and yellow (medium) triage categories.Intervention A prehospital notification application for use by ambulance and emergency clinicians to notify emergency departments (EDs) of an impending arrival of a patient requiring advanced lifesaving care.Main outcome measures The primary outcome was the proportion of eligible patients arriving at the hospital for which prehospital notification occurred. Secondary outcomes were the availability of a trauma cubicle, presence of a trauma team on patient arrival, time to first chest X-ray, and ED and in-hospital mortality.Results Data from January 2017 to January 2018 were collected with 208 patients in the preintervention and 263 patients in the postintervention period. The proportion of patients arriving after prehospital notification improved from 0% to 11% (p<0.001). After the intervention, more patients were managed with a trauma call-out (relative risk (RR) 1.30; 95% CI: 1.10 to 1.52); a trauma bay was ready for more patients (RR 1.47; 95% CI: 1.05 to 2.05) and a trauma team leader present for more patients (RR 1.50; 95% CI: 1.07 to 2.10). There was no difference in time to the initial chest X-ray (p=0.45). There was no association with mortality at hospital discharge (RR 0.94; 95% CI: 0.72 to 1.23), but the intervention was associated with significantly less risk of patients dying in the ED (RR 0.11; 95% CI: 0.03 to 0.39).Conclusions The prehospital notification application for severely injured patients had limited uptake but implementation was associated with improved trauma reception and reduction in early deaths. Quality improvement efforts with ongoing data collection using the trauma registry are indicated to drive improvements in trauma outcomes in India.Trial registration number NCT02877342.