Septic cavernous sinus thrombosis is a rare and potentially life-threatening complication of infections involving the paranasal sinuses or the middle one-third of the face. We report a challenging case of cavernous sinus thrombosis to familiarize otolaryngologists with its clinical features, diagnosis, and management. The patient was a 45-year-old diabetic woman whose signs and symptoms mimicked those of complicated fungal sinusitis. She presented with fever, nausea without vomiting, frontal headache, bilateral ptosis and swelling, double vision, a partial loss of visual acuity in the left eye, and restricted lateral ocular movements. Her Snellen visual acuity had been reduced to 8/10 on the right and 6/10 on the left. Radiologic investigation revealed cavernous sinus extension of sphenoid sinusitis and a fungus-ball appearance in the sphenoid sinus. On the second day of her admission, the patient's vision was further reduced to 6/10 on the right and 2/10 on the left. She then underwent urgent bilateral anterior and posterior ethmoidectomy and sphenoidectomy. At postoperative follow-up, her vision had stabilized at 10/10 bilaterally. At 2 months after discharge, she exhibited no evidence of abducens nerve palsy, and her ocular function had returned to normal. The diagnosis of cavernous sinus thrombosis requires a high index of suspicion and confirmation by imaging. The favorable outcome in our case was attributable to early diagnosis, prompt initiation of appropriate intravenous antibiotic therapy, and surgical drainage by the skillful surgical team.