Basaloid squamous cell carcinoma (BSCC) is a rare tumor representing an aggressive variant of squamous cell carcinoma (SCC) and arising from a common precursor cell. BSCC rarely originates from the sinonasal tract. We report on an 83-year-old woman with BSCC after multiple resections of an inverted papilloma (IP) of the left sinonasal tract. The tumor filled the nasal cavity completely and was infiltrating the ipsilateral frontal skull base and periorbita. Because of the tumor's expansion, the patient's age, and comorbidity, surgery was not performed, but primary radiotherapy was initiated. A possible association between sinonasal BSCC and IP, as implicated by the current case, must be further investigated. In any case, IP requires consequent endoscopic and, if necessary, radiological follow-up in order to detect recurrent disease or malignant transformation.