OBJECTIVE Our aim is to evaluate the effect of nasal septal deviation on the middle ear pressure and Eustachian Tube (ET) functions with regard to the side of deviation. METHODS A prospective randomized clinical trial was conducted. Overall, 50 patients (22 female, 28 male) undergoing septoplasty because of nasal septum deviation were included. The nasal obstruction symptom evaluation (NOSE) scale was used to evaluate surgical satisfaction. Middle ear ventilation and the ET functions of a total of 100 ears were assessed with basal tympanometry and insufflation tests (Valsalva and Toynbee). The tests were performed on the operation day and eight weeks after surgery. The ears were divided into two groups: the affected side (the side of nasal obstruction) (Group 1) and the contralateral side (Group 2). The study parameters obtained before and after septoplasty were compared. RESULTS The NOSE scores decreased after septoplasty (12.48±4.78/7.56±3.4) (p<0.001). There were 20 functional ETs (40%) in the affected side preoperatively, which increased to 36 ears (72%) postoperatively, and functional tubes increased to 35 (70%) from 29 (58%) after surgery in the contralateral side. The changes in the tympanometry results were statistically significant for both the affected side (-33.56 daPA/-21.18 daPA) and contralateral side (29.24daPA/-24.96daPA) (p<0.05), but the alteration in the side of deviation was more evident. CONCLUSIONS Our study shows that septoplasty may have a beneficial effect on middle ear ventilation and ET functions.