Introduction: Postoperative pain after modified radical mastectomy (MRM) increases morbidity, opioid use, and recovery time. Gabapentinoids may reduce central sensitization when administered before surgical injury. This study compared pregabalin and gabapentin as preemptive analgesics in patients undergoing MRM. Patients and Methods: This double-blind randomized controlled trial was conducted at Ngoerah Hospital, Denpasar. Forty-two patients scheduled for elective MRM were allocated to oral pregabalin 150 mg (n = 21) or oral gabapentin 900 mg (n = 21), administered two hours before surgery. The primary outcome was Visual Analogue Scale (VAS) pain score at 12, 24, and 48 hours postoperatively. Secondary outcomes were time to first rescue analgesia and cumulative opioid consumption during the first 24 postoperative hours. Between-group comparisons used the independent t-test or Mann-Whitney U test, as appropriate. Results: Pregabalin produced lower VAS scores than gabapentin at 12 hours (2.18 +/- 0.65 vs 2.65 +/- 0.74; p = 0.034), 24 hours (2.27 +/- 0.66 vs 2.71 +/- 0.63; p = 0.030), and 48 hours (1.90 +/- 0.65 vs 2.36 +/- 0.71; p = 0.033). Time to first rescue analgesia was longer with pregabalin (232.69 +/- 19.88 vs 219.88 +/- 17.81 minutes; p = 0.034), and 24-hour opioid consumption was lower (240 [145] vs 360 [155] micrograms fentanyl equivalent; p = 0.034). No adverse hemodynamic. Conclusion: Preoperative oral pregabalin 150 mg provided statistically superior analgesia and reduced opioid consumption compared with gabapentin 900 mg after MRM. However, the absolute differences in pain scores and rescueanalgesia time were modest; therefore, safety monitoring and larger studies are warranted