Surgical morbidity from open reduction and internal fixation (ORIF) of maxillary sinus wall fracture often surpasses the benefits of ORIF. Hence, the authors devised transnasal endoscopic-assisted reduction of maxillary sinus wall fracture (TERM) without internal fixation as a minimally invasive surgery for maxillary sinus wall fracture. The purpose of this study was to investigate the feasibility of TERM in cadavers and patients. Six cadavers were dissected to evaluate the feasibility of TERM. In addition, 20 patients with maxillary sinus wall fractures who underwent TERM in a tertiary hospital from August of 2013 to December of 2015 were enrolled in this study. Demographic factors, type of anesthesia, computed tomography (CT) scans, clinical characteristics of patients, and patient satisfaction with surgery were analyzed. Cadaveric study showed that endoscopic inferior meatus antrostomy is a feasible method of approaching the maxillary sinus wall in cadavers. In addition, counterforce could be applied to the maxillary sinus wall by pushing packed Vaseline-soaked gauze or using a zygomatic process approach via a Gillies incision. Clinical experience revealed that patients experienced good facial contour restoration postoperatively. The extent of fractured bony segments was reduced on postoperative CT without complications. Patient satisfaction with TERM was greater than that with ORIF (p = 0.031). TERM showed its feasibility in both cadaveric study and clinical study. TERM can be a good alternative to ORIF, especially in patients who are reluctant to undergo a facial incision.