The World Health Organization (WHO) has published guidance recommending systemic corticosteroids for the treatment of patients with severe or critical COVID-19 and no corticosteroids for those with nonsevere COVID-19. Although their recommendations for critical cases were based on the results from seven randomized controlled trials (RCTs), those for noncritical cases were based on the results from only one RCT, the Randomized Evaluation of COVID-19 Therapy (RECOVERY) trial. In search of additional evidence of corticosteroids' effect on COVID-19, we systematically reviewed controlled observational studies, besides RCTs, that assessed the impact of corticosteroid treatment on any type of mortality and/or other outcomes in noncritical patients. Of the 4037 titles and abstracts screened, we ultimately included the RECOVERY trial and five controlled observational studies using propensity score matching, (accessed on September 8, 2020). Two of the controlled observational studies assessed the association between corticosteroid treatment and in-hospital mortality, without finding statistical significance. Four of the controlled observational studies assessed corticosteroids' effect on other outcomes, demonstrating that they were associated with reduced risk of intubation in patients requiring oxygen and with longer hospitalization and viral shedding in mild or moderate cases. These results support the WHO recommendations not to use corticosteroids for nonsevere COVID-19.