Introduction International guidelines provide heterogenous guidance on use of corticosteroids for community-acquired pneumonia (CAP). Methods We performed a systematic review of randomized controlled trials examining corticosteroids in hospitalized adult patients with suspected or probable CAP. We performed a pairwise and dose-response meta-analysis using the restricted maximum likelihood (REML) heterogeneity estimator. We assessed the certainty of the evidence using GRADE methodology and the credibility of subgroups using the ICEMAN tool. Results We identified 18 eligible studies that included 4661 patients. Corticosteroids probably reduce mortality in more severe CAP (RR 0.62 [95% CI 0.45 to 0.85]; moderate certainty) with possibly no effect in less severe CAP (RR 1.08 [95% CI 0.83 to 1.42]; low certainty). We found a non-linear dose-response relationship between corticosteroids and mortality, suggesting an optimal dose of approximately 6 mg of dexamethasone (or equivalent) for a duration of therapy of 7 days (RR 0.44 [95% 0.30 to 0.66]). Corticosteroids probably reduce the risk of requiring invasive mechanical ventilation (RR 0.56 [95% CI 0.42 to 74] and probably reduce intensive care unit (ICU) admission (RR 0.65 [95% CI 0.43 to 0.97]) (both moderate certainty). Corticosteroids may reduce the duration of hospitalization and ICU stay (both low certainty). Corticosteroids may increase the risk of hyperglycemia (RR 1.76 [95% CI 1.46 to 2.14]) (low certainty). Conclusion Moderate certainty evidence indicates that corticosteroids reduce mortality in patients with more severe CAP, the need for invasive mechanical ventilation, and ICU admission.