Background: Orbital apex syndrome is a localized type of orbital cellulitis, where mass lesions occur at the apex of the cranial nerves. Although nasal septal abscess is uncommon, the organism most likely to cause nasal septal abscess is Staphylococcus aureus, and fungal septal abscesses are rare. Here we present an extremely rare and serious case of orbital apex syndrome secondary to fungal nasal septal abscess caused by Scedosporium apiospermum in a patient with uncontrolled diabetes. Case presentation: A 59-year-old man with a 1-month history of headache underwent consultation in an otolaryngological clinic of a general hospital. He was diagnosed with nasal septal abscess and was treated with incisional drainage and 1 month of an antibiotic drip; however, his symptoms persisted. The patient later complained of diplopia due to bilateral abducens nerve palsy, and was then referred to the department of Otolaryngology -Head and Neck Surgery, Kobe City Medical Center General Hospital. The septal lesion was biopsied under general anesthesia, and S. apiospermum was detected using polymerase chain reaction. The patient was treated with an antifungal drug and surgical resection of the lesion was performed. Although the patient survived, he lost his eyesight. Conclusions: This patient represents the second reported case of nasal septal abscess and orbital apex syndrome caused by S. apiospermum. If not treated properly, septal abscess can be life-threatening and cause severe complications, such as ablepsia.