Immune checkpoint inhibitors (ICIs) have been used for various carcinomas. However, immune‐related adverse events have been observed. There have been few reports of treatment with biologics for severe bronchial asthma induced by ICI; therefore, their efficacy is unknown. We report two cases of severe bronchial asthma requiring systemic steroid administration while using anti‐programmed death‐ligand 1 (PD‐L1) antibody for advanced non‐small‐cell lung cancer. The anti‐interleukin‐5 antibody, mepolizumab, was introduced, resulting in the discontinuation of systemic prednisolone and good asthma control. These reports suggest that treatment with biologics may be effective in severe cases of poorly controlled bronchial asthma during ICI therapy.