Immune checkpoint blockers (ICBs) can induce immune-related adverse events (irAEs) whose management is based on expert opinion and may require the prescription of steroids and/or immunosuppressants (ISs). Recent data suggest that these treatments can reduce the effectiveness of ICBs.To investigate the relationship between the use of steroids and/or ISs and overall survival (OS) and progression-free survival (PFS) among ICB-treated patients with an irAE.We prospectively collected data from the medical records of patients with solid tumors or lymphoma in the French REISAMIC cohort and who had been treated with ICBs between June 2014 and June 2020.184 ICB-treated patients experienced at least one Common Terminology Criteria for Adverse Events grade ≥ 2 irAE. 107 (58.2%) were treated with steroids alone, 20 (10.9%) with steroids plus IS, 57 (31.0%) not received steroids or IS. The median OS was significantly shorter for patients treated with steroids alone (25.2 months [95% confidence interval (CI): 22.3-32.4] than for patients treated without steroids or IS (63 months [95%CI: 40.4-NA]) and those receiving an IS with steroids (53.4 months [95%CI: 47.3-NA]) (p < 0.001). The median PFS was significantly shorter for patients treated with steroids alone (17.0 months [95%CI: 11.7-22.9]) than for patients treated without steroids or IS (33.9 months [95%CI: 18.0-NA]) and those receiving an IS with steroids (41.1 months [95%CI: 26.2-NA]) (p = 0.006). There were no significant intergroup differences in the hospital admission and infection rates.In a prospective cohort of ICB-treated patients, the use of IS was not associated with worse OS or PFS, contrasting with the use of steroids for the management of irAEs.