Background: Dry socket is one of the most studied complications in dentistry and several studies have sought an effective and safe method for its prevention and treatment. The aim of this study was to evaluate the effectiveness of intra-alveolar gel chlorhexidine in preventing dry socket after the surgical removal of third molars. Material and Methods: The sample involved the treatment of 40 patients who required extraction of third molars impacted, which were randomly assigned to research groups: experimental group (chlorhexidine gel 0.12%) and control group (placebo gel). Performed the extraction was administered 1 mL of chlorhexidine gel or 1 mL of placebo gel within the socket. The removal of suture was on the fifth postoperative day in which the presence or absence of dry socket was evaluated. Results: No relationship between the appearance of dry socket after application of chlorhexidine gel or placebo gel (X 2 test, p = 0.311) was found. However, significant differences (U Mann-Whitney test, p = 0.036) in the pain presented on the fifth postoperative day were evident (VAS). Conclusions: The administration of intra-alveolar chlorhexidine gel 0.12% could generate a better response to postoperative pain after the removal of third molars.