Ninety-eight patients with chronic primary low back pain were randomized to receive either spinal manipulative therapy (SMT; n=49) or a validated placebo intervention (n=49) delivered 12 times over 4 weeks. The primary outcome was change in pain intensity and disability. Secondary outcomes included pressure pain thresholds (PPTs), pain catastrophizing, central sensitization, depression, and anxiety. Outcomes were assessed at baseline, 4 weeks, 8 weeks, and 16 weeks. Overall, the results revealed a significantly greater reduction in pain intensity in the SMT group versus placebo, but no significant difference in disability. Segmental hyperalgesia and pain catastrophizing were also reduced with SMT. These findings suggest SMT provides clinically meaningful pain relief, potentially via modulation of nociplastic mechanisms such as hyperalgesia.