Background: Sphenoid sinus mucocele (SSM) represents a relatively rare disease among pediatric population as compared to adults, with a 1% to 3% incidence of all paranasal sinus mucoceles. Since the initial symptoms varied often, SSM caused blindness was scarcely seen. Case Presentation: Here we described an unusual case of small, isolated SSM causing acute visual loss in a 9-year-old girl. The patient first consulted an ophthalmologist for her right blindness. A diagnosis of SSM was suspected indicated by an orbital MRI scan. Thereafter the patient was referred to our department and an endoscopic sphenoidotomy and optic nerve decompression was performed. Surprisingly, her vision was relieved immediately after surgery, followed by dramatic improvement during the postoperative 20-month follow-up period. Conclusion: To our knowledge, a better understanding of SSM in pediatrics is essential for clinicians, including neurologists, ophthalmologists, and otolaryngologists to make early diagnoses and correct treatment by MRI and CT scan. Prompt surgical intervention of endoscopic transnasal sphenoidectomy is a quite safe, effective, and minimally invasive method for patients.