Background. Community-acquired pneumonia (CAP) is a common condition, with mortality increasing in patients who require intensive care unit (ICU) admission. A better understanding of the current aetiology of severe CAP will aid clinicians in requesting appropriate diagnostic tests and initiating appropriate empiric antimicrobials. Objective. To assess the comorbidities, aetiology and mortality associated with severe CAP in a tertiary ICU in Cape Town, South Africa. Methods. We retrospectively analysed a prospective registry of all adults admitted to the medical intensive care unit at Tygerberg Hospital with severe CAP over a 1-year period. Results. We identified 74 patients (mean (SD) age 40.0 (15.5) years; 44 females). The patients had a mean (SD) APACHE II score of 21.4 (7.9), and the mean ICU stay was 6.6 days. Of the 74 patients, 16 (21.6%) died in ICU. Non-survivors had a higher mean (SD) APACHE II score than survivors (28.3 (6.8) v. 19.4 (7.1); p<0.001). Mycobacterium tuberculosis (n=16; 21.6%) was the single most common agent identified, followed by Pseudomonas aeruginosa (n=9; 12.2%). All P. aeruginosa isolates were sensitive to first-line treatment. No organism was identified in 32 patients (43.2%). Conclusion. M. tuberculosis was the single most common agent identified in patients presenting with CAP. The mortality of CAP requiring invasive ventilation was relatively low, with a strong association between mortality and a higher APACHE II score.