The introduction of Emergency Medicine in Rwanda in 2015 has been associated with a mortality reduction in patients presenting to Kigali University Teaching Hospital (KUTH). In the context of increasing numbers of critically ill patients presenting to Emergency Departments (ED) globally, the aim of this study was to describe the characteristics of critically ill patients, the critical care interventions performed, and the outcomes of critically ill patients presenting to the KUTH ED with the goal of informing future research into the root causes of mortality of critically ill ED patients and of identifying high yield topics for didactic and procedural training. A descriptive observational prospective cohort pilot study analyzed all patients ≥15 years who presented to KUTH between April and June 2022 with modified South African Triage Scores of Red with alarm, Red without alarm, and Orange. Of 320 patients, 66.9% were male and median age was 40 years. Patients were triaged as Orange (65.3%), Red without alarm (22.8%), and Red with alarm (11.9%). Presentations were categorized as: medical emergencies (48.0%), traumatic injury (44.5%), and surgical emergencies (7.6%). Median length of stay was 31h (IQR 28, 56) and boarding was 23h (IQR 8, 48). Overall mortality was 12.2% and highest among medical emergencies (16.5%, p = 0.048) and increased significantly with triage color: Red with alarm (47.4%), Red without alarm (16.4%), and Orange (4.3%, p < 0.0001). Cardiopulmonary resuscitation (CPR) (10.3%), endotracheal intubation (8.8%), and vasopressor administration (3.1%) were the most frequent critical interventions performed. Survival after cardiac arrest was 9.1% and 32.1% after intubation. Mortality was associated with the following interventions: CPR, intubation, and use of vasopressors (p < 0.05). This pilot study identified the most common critical care interventions performed and a high mortality among patients who required these interventions in the ED of a tertiary teaching hospital in Rwanda. These findings will inform didactics and procedural training for emergency care providers. Future research should focus on the root causes of mortality in these specific patient populations and identify areas of system strengthening to reduce mortality.