Abstract Corticosteroids are commonly used for the management of severe toxicities associated with chimeric antigen receptor (CAR) T-cell therapy. However, it remains unclear whether their dose, duration, and timing may affect clinical efficacy. Here, we determined the impact of corticosteroids on clinical outcomes in patients with relapsed or refractory large B-cell lymphoma treated with standard of care anti-CD19 CAR T-cell therapy. Among 100 patients evaluated, 60 (60%) received corticosteroids for management of CAR T-cell therapy–associated toxicities. The median cumulative dexamethasone-equivalent dose was 186 mg (range, 8-1803) and the median duration of corticosteroid treatment was 9 days (range, 1-30). Corticosteroid treatment was started between days 0 and 7 in 45 (75%) patients and beyond day 7 in 15 (25%). After a median follow-up of 10 months (95% confidence interval, 8-12 months), use of higher cumulative dose of corticosteroids was associated with significantly shorter progression-free survival. More importantly, higher cumulative dose of corticosteroids, and prolonged and early use after CAR T-cell infusion were associated with significantly shorter overall survival. These results suggest that corticosteroids should be used at the lowest dose and for the shortest duration and their initiation should be delayed whenever clinically feasible while managing CAR T-cell therapy–associated toxicities.