Septic cavernous sinus thrombosis (CST) is a rare, life-threatening condition that commonly originates from sinusitis. Posterior nasal septal abscess (NSA) is an extremely rare cause of septic CST because it is a very rare condition by itself. Here we report a rare case involving an elderly woman with septic CST associated with a posterior NSA that was successfully treated without any sequelae. Incision and drainage of the posterior NSA were performed under local anesthesia, and the nasal packing was removed 2 days postoperatively. Pus from the abscess was sent for culture and sensitivity analyses, which revealed Enterococcus faecium . She was treated with intravenous (IV) third-generation cephalosporin (2 g twice daily) and IV vancomycin (0.75 g twice daily) for 4 weeks. IV low-molecular-weight heparin was administered at a dose of 40 mg twice daily for 4 days, followed by warfarin (3 mg once a day) for 21 days. The patient was discharged without any sequelae after 4 weeks. At the 2-month follow-up, she did not complain of any further symptoms. The findings from this case suggest that clinicians should maintain a high index of suspicion and provide prompt treatment to prevent mortality and morbidity associated with septic CST.