We present the case of a 70-year-old female patient who sought consultation with an otolaryngologist due to a mass protruding from the left nasal cavity. The patient reported that she had noticed the mass for the past two months, although she had experienced nasal breathing difficulties for over ten years. Upon examination, a large pink mass was observed protruding from the left nostril. Anterior rhinoscopy revealed complete obstruction of both the left and right nasal cavities by the tumor mass. Computed tomography showed that the mass entirely filled both nasal cavities and all paranasal sinuses. Surgical treatment was performed, involving endoscopic sinus surgery, which resulted in the complete removal of the mass. Histopathological analysis confirmed that the mass was a case of massive sinonasal polyposis. At the six-month follow-up, no signs of recurrence were observed. Although sinonasal polyposis is a relatively common condition in rhinologic surgery, such pronounced polyposis with prolapse of polyps through the nostril is a rare presentation that can initially mimic benign or malignant tumors of the nasal cavities.