Lumbar spinal stenosis (LSS) is a common degenerative disease of the spine in older adults that often requires surgery and long-term drug therapy. This nationwide retrospective cohort study analyzed data from 2015 on patients with newly diagnosed LSS. The Korean medicine (KM) group included patients with at least 3 outpatient visits to KM within a year of diagnosis and combined with Western medicine. The control group had at least 3 Western medicine visits without CM. After propensity score matching (PSM), 70,897 pairs were included for surgical data and 17,217 patients per opioid group. CM treatment was associated with a lower risk of lumbar surgery (HR: 0.821; 95% CI: 0.782–0.862), opioid use (HR: 0.810; 95% CI: 0.752–0.872), and additional opioid use (HR: 0.630–0.919). The findings suggest that CM reduces the long-term risk of surgery and opioids in patients with LSS and may be a conservative option. Randomized controlled trials are needed for confirmation.