The patient was a 69-year-old man diagnosed with stage ⅣB lung adenocarcinoma with 95% programmed death- ligand 1 expression, and pembrolizumab monotherapy was initiated. The patient exhibited fatigue from the 12th course(36 weeks after treatment initiation) of treatment. Chest computed tomography revealed scattered ground-glass opacities in the upper lobes of both lungs, and he was subsequently diagnosed with interstitial pneumonia. Fatigue persisted even after a drug holiday from pembrolizumab, and the patient was diagnosed with hypopituitarism based on the results of endocrinological examinations. Rashes appeared on both legs 40 weeks after treatment initiation, which led to the patient being diagnosed with a drug-induced skin disorder. All the adverse events resolved upon treatment with hydrocortisone. Immune- related adverse events due to pembrolizumab may occur in multiple organs simultaneously.