This is a case with lung adenocarcinoma treated with chemotherapy and pembrolizumab presented with cough and throat irritation. Over the subsequent two months, the cough worsened and then persisted despite antibiotics. Computed tomography showed no changes in the lung parenchyma, but revealed thickening of the trachea and central bronchi. Erythematous mucosa was seen in these areas on bronchoscopic evaluation, and a tracheal biopsy showed infiltrating lymphocytes and plasma cells without evidence of malignancy or pathogens. As alternative causes had not been discovered, she was diagnosed with pembrolizumab-induced tracheobronchitis. Treatment with prednisone and an inhaled corticosteroid resulted in rapid improvement of symptoms and airway abnormalities on imaging. Airways disease related to immune checkpoint inhibitor toxicity is a rare cause of respiratory symptoms, but should be considered after exclusion of more common etiologies.