Studies suggest the burden of non-hospitalized severe respiratory illness might be substantial in Kenya. Using data from a Kenya COVID-19 vaccine effectiveness evaluation, we compared characteristics of patients aged ≥12 years who were hospitalized with severe respiratory illness to outpatients who were referred for hospitalization and declined (non-hospitalized). Symptom presentation and lung radiograph findings were similar among both groups, and patients in both were diagnosed with critical conditions, including acute respiratory distress syndrome (12% hospitalized; 4% non-hospitalized) and sepsis (10% both). Findings underscore the importance of including non-hospitalized severe illness when estimating the burden of disease for respiratory viruses. © 2025 Elsevier B.V., All rights reserved.