We report a rare case of squamous cell carcinoma (SCC) of the nasal cavity arising in a patient with granulomatosis with polyangiitis (GPA). The patient was a 35-year-old man who had been diagnosed 15 years earlier with GPA and treated medically for sinonasal, pulmonary, and renal involvement. He presented to us with left-sided orbital and cheek pain and nasal obstruction. Endoscopy detected a friable, exophytic mass that involved the left lateral nasal wall and septum. Biopsy analysis identified the mass as an SCC. A definitive endoscopic resection was performed, followed by chemoradiation, but the patient exhibited progression of disease 2 months after the cessation of therapy. He then underwent an open craniofacial resection and a second round of chemoradiation. At 7 months of follow-up, he remained disease-free. Sinonasal symptoms in GPA are consistent with those in chronic rhinosinusitis, but the presence of unilateral symptoms may suggest a neoplastic process. Immunosuppressants are implicated in the pathophysiology of this malignancy, but equally plausible is the oncogenic role of chronic inflammation.