Background: To explore the association between the use of prehospital medications and the development of fatal outcomes in patients who required hospitalization due to coronavirus disease-2019 (COVID-19). Methods: This retrospective cohort study included adult patients who were hospitalized due to COVID-19. Demographic, clinical, and laboratory data, prehospital medication history, and fatal outcome development (use of high-flow oxygen therapy, intensive care unit [ICU] admission, or mortality) were extracted from the medical records of patients who were admitted due to COVID-19 to the Carlos Seguín Escobedo National Hospital of Arequipa, Peru during July to September 2021, the period after the second wave of COVID-19 cases in Peru. Survival was analyzed using the Cox proportional hazards model, and crude hazard ratios and adjusted hazard ratios (aHR) with their respective 95% confidence intervals (95% CI) were calculated. Results: A total of 192 patients were evaluated, of whom 62% were males and 46.9% did not require oxygen support at admission. Additionally, 64.6% used nonsteroidal anti-inflammatory drugs, 35.4% used corticosteroids, 28.1% used macrolides or ceftriaxone, 24.5% used ivermectin, and 21.9% used warfarin before hospitalization. Of the patients, 30.2% developed a fatal outcome during follow-up. The multivariate analysis revealed that prehospital corticosteroid use was independently associated with the fatal outcome due to COVID-19 with an aHR = 5.29 (95%CI: 1.63–17.2). Conclusion: Prehospital corticosteroid use was associated with a 5-fold increased risk of fatal outcome development.