Background: Many techniques have been proposed to close an oroantral fistula (OAF), with most of them involving transoral repairs with oral soft tissue flaps. An additional Caldwell-Luc approach or endoscopic sinus surgery (ESS) is required to address coexisting maxillary sinusitis. Objectives: This study presents the endonasal closure of an OAF through modified endoscopic medial maxillectomy (MEMM) with a free nasal mucoperichondrial-osteal graft. Materials and methods: Sixteen OAF patients who underwent closure operations in our department from May 2013 to June 2018 were retrospectively reviewed. Results: The main cause of OAF was maxillary dental cysts (56.25%). The OAF size ranged from 2 x 2 to 10 x 15 mm. The first molar (62.5%) was the most frequently involved tooth. All closures were made via MEMM, using nasal mucoperichondrial-osteal grafts harvested from the septum or nasal base. All patients were followed up for at least six months. Successful closure after a single procedure was achieved in 93.75% of cases. No obvious complications or recurrences were observed. Conclusions: Endonasal repair of OAFs via MEMM with free nasal mucosal grafts is feasible and promising. The approach preserves the normal oral and nasal physiology after surgery. It could be used alone for the closure of small to medium-sized OAFs.