Mucocele of the sphenoid sinus is a rare disease, and its clinical manifestations are varied, primarily reflecting the close anatomical relationship between the sphenoid sinus and contiguous neurologic and vascular structures. So it is frequently misdiagnosed as pituitary or skull base tumors. Therefore, correct diagnosis and surgical approach greatly influences the prognosis of the patients and helps to avoid unnecessary surgical procedures. We report a case of sphenoid sinus mucocele that was characterized by sudden visual loss.