Cytokine release syndrome (CRS) is a systemic inflammatory disease caused by a variety of factors, including infections and certain drugs. A 70-year-old man who was diagnosed with a postoperative recurrence of lung adenocarcinoma received nivolumab, ipilimumab, pemetrexed and carboplatin every 3 weeks for two cycles followed by nivolumab and ipilimumab, which resulted in a partial response. Four days after the dose of nivolumab, the patient returned with diarrhea and fever. The patient was diagnosed with COVID-19 infection accompanied by severe colitis. Although intensive care was performed, the patient suddenly went into cardiopulmonary arrest. Examination revealed an abnormally high interleukin-6 level, suggesting CRS. This is the first report of a patient with CRS accompanied with COVID-19 infection during treatment with ICIs. Cytokine release syndrome (CRS) is a systemic inflammatory disease caused by a variety of factors, including infections and certain drugs. Here, we report a case of non-small cell lung cancer with CRS caused by COVID-19 infection during treatment with nivolumab and ipilimumab. Fever is a common event in cancer patients, especially in COVID-19-infected patients, but when fever develops during cancer immunotherapy, CRS should always be kept in mind.