A mucocele is an epithelial–lined, mucus–containing sac that can fill the sinus completely and expand gradually. When the mucocele content becomes infected, the lesionis termed mucopyocele. A 38 years old man presented to our tertiary center with one month history of swelling right cheek associated with decreased vision. Computed tomography images revealed a well defined soft tissue mass in right maxillary sinus with distortion of osteometal complex extending to extraconal infraorbital region. MRI suggestive of mucocele with secondary infection and hypoplastic maxillary sinus. Under general anesthesia, surgical decompression of the maxillary mucopyocele through an endoscopic approach was done. Postoperatively his visual acuity returned to normal and postoperative period was uneventful. The diagnosis of mucocele is usually made by CT imaging of the paranasal sinuses. Endoscopic sinus surgery is an effective treatment modality for maxillary sinus mucocele with favorable long–term outcome