Mucoepidermoid carcinoma (MEC) is one of the common malignant tumors of the salivary glands, with fewer than 200 cases reported in the nasal cavity and paranasal sinuses. Sinonasal inverted papilloma (SNIP), a benign epithelial tumor originating from Schneiderian mucosa, has the potential for recurrence and malignant transformation, with squamous cell carcinoma being the most common type of malignant transformation, while MEC is extremely rare. The Department of Otorhinolaryngology at the Affiliated Hospital of Inner Mongolia Medical University treated a patient with recurrent SNIP that had transformed into MEC. The Department of Otorhinolaryngology at the Affiliated Hospital of Inner Mongolia Medical University admitted a patient with recurrent inverted papilloma of the nasal cavity and paranasal sinuses that had malignant transformed into mucoepidermoid carcinoma. The patient underwent endoscopic endonasal resection of the nasal and sinus tumor, with a favorable postoperative recovery and no recurrence observed during follow-up to date. Immunohistochemistry (IHC) results showed overexpression of EGFR protein in the tumour tissue, and fluorescence in situ hybridisation (FISH) results showed no MAML2 gene fusion, suggesting that the recurrence and malignant transformation of this case of inverted papilloma of the nasal cavity and sinuses into mucoepidermoid carcinoma is associated with EGFR protein overexpression and not with MAML2 gene fusion.