SMARCB1 (INI-1)-deficient sinonasal carcinoma is a rare, poorly differentiated, and locally aggressive neoplasm. Frequently, this disease entity mimics benign head and neck conditions, making diagnosis and management challenging. We report the case of a 66-year-old female who presented with a right nasal mass on endoscopy. Microscopy revealed well-defined nests of plasmacytoid tumor cells infiltrating a desmoplastic stroma, with areas of necrosis and focal hemorrhage. Based on the histomorphology and immunohistochemistry studies, the case was signed out as SMARCB1 (INI-1)-deficient sinonasal carcinoma. This is the first reported case in the Philippines based on a search of local journal databases. Recent advancements in therapeutics highlight the importance of providing molecular characterization of these tumors.