A 71-year-old patient with non-small cell lung carcinoma was treated with nivolumab. After 10 months of treatment, the patient presented with generalized weakness, polyuria, and polydipsia with plasma glucose of 471 mg/dL (26.2 mmol/L), HbA1C of 7.8%, and no ketone bodies. The patient was diagnosed with nivolumab-associated T1DM and treated with insulin and intravenous fluids. Here, INS is linked to non-small cell lung carcinoma.