To evaluate the effectiveness of employing the water sac dilation (WSD) method during endoscopy-assisted transoral resection of parapharyngeal space benign tumor (PSBT). Between February 2017 and January 2022, a total of 32 patients diagnosed with PSBT were included in this prospective study and were randomly allocated into two groups: the WSD group and the control group. Tumors of the WSD group patients were all dissected using the WSD method. The final numbers of studied patients in WSD group and control group were 17 and 15, respectively. The basic information was comparable between these two groups of patients. All these patients successfully underwent tumor resection via transoral approach. The operation time, intraoperative blood loss, drainage volume on the first postoperative day, drainage duration, and the total drainage volume in the WSD group patients were significantly lower than those in the control group patients (all p < 0.05). No surgical complications occurred, and no residual tumor or recurrence could be identified at 6 months after surgery in both groups of patients. The application of the WSD method in endoscopy-assisted transoral resection of PSBT effectively attenuated intraoperative injury, improved surgical efficiency, and accelerated postoperative recovery. 3 Laryngoscope, 2024.