Background: Infratemporal fossa abscess following odontogenic infection is not rare, and usually occurs as a sequela of dental disease. Infratemporal fossa abscess was previously treated with the combination of buccal incision and temporal incision, or via a transoral approach. Method: This paper reports a case of infratemporal fossa abscess in a 51-year-old female. Results: The abscess was drained transnasally via an endoscopic modified medial maxillectomy approach, preserving the inferior turbinate and nasolacrimal duct. The pain remitted the next day and trismus had diminished in one week. Conclusion: The transnasal approach with endoscopic modified medial maxillectomy is a direct, minimally invasive method that provides a direct field of view for drainage of infratemporal fossa abscess. This approach is recommended for infratemporal fossa abscess.