Methods: LSS patients with predominant NIC symptoms for ≥3 months were randomized (1:1:1) to receive GBA (1,800 mg/day), PGB (300 mg/day), or placebo in addition to standard conservative management, including physical therapy and naproxen. GBA and PGB were both titrated to the effective dose over 14 days. The primary outcome was NIC pain measured by Visual Analog Scale (VAS). Secondary outcomes included the Swiss Spinal Stenosis Score (SSS), self-paced shuttle walk test (SPSWT; time to NIC symptoms and walking distance), Euro-QoL Group’s 5-Dimension, 5-Level (EQ-5D-5L), and adverse effects. All outcomes were assessed monthly over 4 months. Results: Ninety patients (mean age, 63.14 years; symptoms duration, 19.38 months) were included. All groups demonstrated significant improvements in VAS, SSS, SPSWT, and EQ-5D-5L at 4 months. At 1 and 2 months, PGB showed greater EQ-5D-5L improvement compared to GBA (mean differences: 0.07 [p=0.045] and 0.08 [p=0.001], respectively). No significant differences in other outcomes were observed between groups at any time point. Adverse effects, including dizziness and sedation, were more common in the GBA and PGB groups compared to placebo (p<0.001). Conclusions GBA and PGB did not demonstrate superior efficacy over placebo in reducing NIC and improving functional outcomes in LSS. Moreover, their use was associated with a higher incidence of adverse effects. These findings suggest limited utility for gabapentinoids as adjunctive treatments for LSS.