Objective: The aim of the study was to compare the effect of submucosal injection of dexamethasone and triamcinolone acetonide on postoperative pain, swelling, and trismus occurring after impacted mandibular third molar surgery. Method and Materials: A total of 78 patients (aged 18 to 35) with asymptomatic, unilateral, impacted mandibular third molar, and without any systemic disease were included in this study. Patients were divided into three groups randomly (control, dexamethasone, and triamcinolone acetonide). In the experimental groups, dexamethasone and triamcinolone acetonide were injected into submucosa at about 1 cm above the surgical area submucosally. The control group of patients did not take any drug submucosally but the same surgical procedure was applied. Pain evaluation was performed by visual analog scale (VAS). Swelling was measured using a flexible standard ruler measuring the dimensions of the axes between certain points on the face. For trismus evaluation, maximum mouth opening was measured. Measurements taken on the preoperative, and on postoperative first, third, and seventh days were compared with each other and statistically evaluated. Results: There were statistically significant differences between the control and experimental groups on the different days of the postoperative period. The effect of triamcinolone acetonide on pain started on the first day postoperatively and the effect of triamcinolone acetonide on trismus and pain was better than other groups at the third and seventh days. However, there was no statistically significant difference between the effects of dexamethasone and triamcinolone acetonide regarding postoperative complications. Conclusion: The submucosal injection of dexamethasone or triamcinolone acetonide might be an effective treatment for postoperative discomfort occurring following impacted mandibular third molar surgery, and triamcinolone acetonide could be applied as an alternative to dexamethasone. Keywords: submucosal dexamethasone, submucosal triamcinolone acetonide, third molar surgery