OBJECTIVE Breast cancer surgery is associated with acute and chronic pain. We sought to systematically evaluate the effects of gabapentin and pregabalin on postoperative pain among patients undergoing breast cancer surgery. METHODS We searched MEDLINE, EMBASE, CENTRAL, Web of Science, and ProQuest from the inception of each database to November 2015. We included studies enrolling adult patients undergoing breast cancer surgery who were randomly assigned to preoperative gabapentin or pregabalin versus placebo or active control and assessed acute (≤24 h) or chronic (≥2 months) pain. We conducted meta-analyses when possible and rated the quality of evidence (QoE) by using the GRADE approach. RESULTS Twelve studies were eligible for review, of which eight evaluated gabapentin (n = 516) and four pregabalin (n = 209). Gabapentin reduced pain scores in the recovery room (mean difference [MD] -1.68 on a 0-10 Numeric Rating Scale (NRS), 95% CI -2.59 to -0.77; minimally important difference is 1 point; relative risk [RR] for mild pain (<4/10) 1.71, 95% CI 1.33-2.02; moderate QoE) and 24 h postoperatively (MD -0.52, 95% CI -1.02 to -0.01; RR for mild pain 1.07, 95% CI 1.00-1.13; very low QoE). Pregabalin reduced pain and morphine consumption in the recovery room (MD -6.71 mg, 95% CI -10.73 to -2.70; low QoE). No significant difference was observed in pain score at 24 h (MD -0.38, 95%, CI -0.96 to 0.21; moderate QoE). Neither drug reduced the rate of chronic postoperative pain. CONCLUSIONS Gabapentin and pregabalin seem to reduce opioid consumption in the recovery room. Gabapentin, but not pregabalin, reduces pain at 24 h after breast cancer surgery. Neither drug affects the development of chronic postoperative pain. CONCLUSIONS Gabapentin and pregabalin administered perioperatively in patients undergoing breast cancer surgery improve acute postoperative pain as indicated by the reduction in opioid consumption. Further data are needed on reducing chronic postoperative pain.