Objective: Endodontic treatment generally results in a wide range of postoperative pain intensity. The aim of this study was to investigate the effect of preoperative acupuncture on postoperative pain in molar teeth with symptomatic apical periodontitis. Method and Materials: Thirty patients having symptomatic apical periodontitis with a preoperative and percussion pain of visual analog scale (VAS) more than 60 were included in this study. The patients were randomly distributed into two groups; G1, real acupuncture; and G2, placebo (mock acupuncture). After 15 minutes of application, root canal treatment was performed. A logistic regression analysis was used to determine the variable(s) (group, age, gender, tooth number, preoperative pain, preoperative percussion pain, and radiographic status) that controls the postoperative pain significantly. Chi-square, Mann Whitney U, and independent t tests were performed to analyze the data, and the level of significance was set at .05 (P = .05). Results: A regression analysis demonstrated that the group variable had the most significant effect on postoperative pain at day 1 (P = .003). Results showed that acupuncture reduced the preoperative and percussion pain levels significantly more than placebo group at all day intervals (P .05). For postoperative pain at the 7-day follow-up, the pain ranged from "mild" to "no pain" in G1, compared with "moderate" to "minimal" in G2. Only one patient required postoperative analgesics in the acupuncture group compared to eight patients for placebo. Conclusions: Preoperative acupuncture can be beneficial in reducing postoperative pain in teeth with symptomatic apical periodontitis. Keywords: acupuncture, apical periodontitis, endodontics, postoperative pain, root canal