Recent studies suggest gabapentin has opioid-sparing effects and may reduce acute postoperative pain. However, there is limited research on the efficacy of gabapentin when combined in a multimodal approach after shoulder arthroscopy under general anesthesia with an interscalene block. We conducted prospective, double-blind study of 70 patients who were randomized to receive either 300 mg of gabapentin or placebo 1 hour before surgery, then twice a day for 2 days. The primary outcome was average pain scores. Secondary outcomes included differences in morphine equivalents, adverse effects, and sleep patterns. No significant differences in pain scores were found on day 1 (gabapentin mean [SD], 4.23 [2.61], vs placebo, 4.61 [2.57]; P = .58) or day 2 (gabapentin, 4.26 [2.39], vs placebo, 4.03 [2.34]; P = .71). Total morphine equivalents on day 1 (gabapentin, 9.75 mg [6.58 mg], vs placebo, 9.52 mg [4.75 mg]; P = .88) and day 2 (gabapentin, 9.21 mg [6.66 mg], vs placebo, 6.93 mg [5.44 mg]; P = .17) were similar. Adverse effects and sleep patterns were similar (P > .05). These results suggest this dosing regimen of gabapentin is not efficacious in improving outcomes in patients undergoing shoulder arthroscopy under general anesthesia with an interscalene block.