Aim: This study aims to evaluate the efficacy of tranexamic acid on the incidence of DS following lower third molar surgery. Subjects and methods: Twenty patients with symptomatic impacted mandibular third molar were extracted. Patients were randomly allocated into two groups. In group A; gelfoam soaked in 5% tranexamic acid solution was placed in the socket after extraction. In group B, gelfoam soaked in saline was placed in the socket. Pain, bleeding, edema and trismus were evaluated on the 2nd, 4th, 7th and14th postoperative days. Results: Results have indicated that the incidence of DS was20% in group B in whereas in group A it was0%. Postoperative pain was significantly lesser in group A than group B at the day of surgery,2nd and 4th postoperative days. At the 7th and 14th days the difference was nonsignificant. TXA has no effect on the mouth opening and postoperative swelling following lower third molar surgery. Conclusion: Intra socket application of TXA after mandibular third molars surgery may help reduce the incidence of DS.TXA is more effective than gelfoam for prevention of DS. Intra socket application of TXA decreased the intensity of pain especially in the early postoperative days.