The last decade has seen the emergence of immune checkpoint inhibitors for the treatment of a wide variety of cancer types. While these medications are generally speaking well tolerated, the full long-term side effect profiles of these medications have not been fully elucidated. We describe a case of chronic rhinosinusitis with nasal polyposis induced treatment with pembrolizumab, the first reported case. We present the case of a 48-year-old man with a background history of stage IV non-small cell lung cancer with bone metastases. He was commenced on pembrolizumab and over the course of the subsequent 5 years he developed significant nasal polyps bilaterally, and was commenced on medical therapy. Sinus CT scan demonstrated bilateral total opacification of all his sinuses and nasal cavity. He subsequently underwent bilateral functional endoscopic sinus surgery. He remains symptom-free and at his last clinical follow-up visit 1 year later. There are limited case reports of nasal polyposis occurring in patients receiving immune checkpoint inhibitors, with only one case requiring surgery. We describe the first case of severe nasal polyps due to pembrolizumab and successfully treated with polypectomy. From our review, there were no cases that required a cessation of therapy.