OBJECTIVES: The purpose of this study was to evaluate the analgesic effects of perioperative gabapentin on postoperative acute and chronic pain after coronary artery bypass graft (CABG) surgery with median sternotomy and internal mammary artery harvesting. DESIGN: A double-blind randomized clinical study. SETTING: A single-academic hospital. PARTICIPANTS: Patients with ischemic heart disease who were scheduled to undergo CABG surgery. INTERVENTIONS: Forty patients were allocated randomly into 2 groups; the gabapentin group (n = 20) received 1.2 g/d of oral gabapentin before and for 2 days after surgery, and the placebo group (n = 20) received a placebo capsule instead. The primary outcome was to evaluate the effects of gabapentin on acute and chronic pain after surgery. The postoperative evaluation included the assessment of pain at rest and when coughing, intravenous tramadol usage, postoperative morbidities, and side effects of gabapentin. Postoperative analgesia at 6, 12, 18, 24, 48, and 72 hours after extubation and at discharge was evaluated with the visual analog scale. The assessment of postoperative pain at the 1- and 3-month follow-ups was performed using a numeric rating scale. MAIN RESULTS: Postoperative pain scores at 1, 2, and 3 days were significantly lower in the gabapentin group when compared with the placebo group (p < 0.05). Pain scores at 1 and 3 months postoperatively were lower in the gabapentin group than in the placebo group (p > 0.05). Consumption of intravenous tramadol given as rescue analgesic within 24 hours after extubation in the gabapentin group was 99.0 ± 53.8 mg versus 149.4 ± 72.5 mg in the placebo group (p < 0.05). There were no differences in the incidence of side effects and time to extubation between the groups. CONCLUSIONS: Gabapentin significantly reduced the intensity of pain and tramadol consumption in the early postoperative period after CABG surgery. Pain scores at 1 and 3 months after surgery were low in both groups, with no significant difference between the groups.