A 55-year-old man with stage IV lung adenocarcinoma was treated with cisplatin, pemetrexed, nivolumab, and ipilimumab. Approximately 100 days after treatment initiation, he became disoriented and presented to the emergency department with a high fever. Blood tests revealed liver and kidney dysfunctions. Subsequently, the patient developed generalized convulsions that required intensive care. He was clinically diagnosed with cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS). Organ damage was gradually controlled with immunosuppressive drugs, including steroids, and the patient was discharged. Successful treatment is rare in patients with CRS, including ICANS, during immune checkpoint inhibitor treatment for solid tumors.