Objective: We aimed to investigate the extent of pulmonary involvement and adverse outcomes in patients receiving angiotensin-converting enzyme inhibitor (ACEI)/ angiotensin II receptor blocker (ARB) versus who did not, in hospitalized coronavirus infectious disease 2019 (COVID-19) patients. Methods: All COVID-19 patients with a positive polymerase chain reaction (PCR) test, who were admitted to our tertiary referral hospitals in Tehran, Iran between January 2021 and May 2021, and had an on-admission chest computed tomography (CT) scan, were included. The patients were divided into two groups (receiving ACEI/ARB and who did not) for further analysis. The outcomes of interest in our study were the extent of pulmonary involvement, intensive care unit (ICU) admission, and death. Results: A total of 893 participants (mean age of 58.6±15.4 years; female, 522 (58.4%)) were enrolled. Among them, 368 (41.2%) participants had hypertension, and use of ACEI/ARB was reported in 183 (20.5%) participants. Of all, 409 (45.8%) participants required ICU admission, and 259 (29%) participants succumbed to death. We found that participants who received ACEI/ARB were less likely to progress critical disease and experienced significantly lower ICU admission (P=0.022) and death (P<0.001). On multivariable analysis adjusting for age, sex, and comorbidities, this relationship remained statistically significant for death [OR: 0.23 (0.14-0.38); P<0.001] and ICU admission [OR: 0.49 (0.32-0.73); P=0.001]. Conclusion: Our findings showed that COVID-19 patients who receiving ACEI/ARB prior to hospitalization vs. those who did not, had more favorable outcomes.