To examine the effects of laser moxibustion on pain and function in patients with knee osteoarthritis.A double-blind randomized clinical trial (4-week treatment, 20-week follow-up) was conducted. A total of 392 symptomatic knee osteoarthritis patients with moderate or greater clinically significant knee pain were randomly assigned to laser treatment or sham laser control group (1:1). Twelve sessions of laser moxibustion treatments or sham on the acupuncture points at the affected knee(s) were performed three times a week for 4 weeks. The primary outcome measurement was change in WOMAC pain score from baseline to week 4.Among the 392 randomized participants, 364 (92.86%) completed the trial. The median WOMAC pain score significantly decreased at week 4 in the active group than in the sham group (2.1; 95% CI, 1.6 to 2.6; P < .01). At week 24, compared to the sham laser, active laser treatment resulted in significant pain reduction and function improvement (3.0; 95% CI, 2.5 to 3.6; P < 0.01, and 14.8; 95% CI, 11.9 to 17.6; P < .01, respectively). The physical component of the quality of life significantly improved in the active group than in the sham control at week 4 (3.2; 95% CI, 1.3 to 5.0; P = 0.001) up to week 24 (5.1; 95% CI, 3.3 to 7.0; P < .001). No serious adverse effects were reported.Laser moxibustion resulted in statistically and clinically significant pain reduction and function improvement following a 4-week treatment in patients with knee osteoarthritis.