<p>This study investigated changes in neurological grades and plasma biomarker levels, including hypoxia-inducible factor-1α (HIF-1α), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and total plasma NAD(H) levels, in dogs with thoracolumbar intervertebral disc disease (TL-IVDD) undergoing acupuncture treatment. A total of 46 treatment episodes from 36 dogs with TL-IVDD were included in the neurological assessment. Plasma biomarker analyses were performed using available paired samples after exclusion of missing values and incomplete paired observations. Neurological grades improved after acupuncture treatment, with significant reductions observed in dogs treated with electroacupuncture during both the acute and preventive phases. Plasma TNF-α concentrations showed significant treatment period-, disease phase-, and treatment method-dependent changes, with significant Pre–Post differences observed in the electroacupuncture group during both phases. Plasma IL-6 concentrations showed more limited changes, with a significant Pre–Post difference detected only in the classical needle acupuncture group during the acute phase. In contrast, total plasma NAD(H) levels and plasma HIF-1α concentrations did not show significant treatment-related changes. These findings suggest that acupuncture treatment, particularly electroacupuncture, was associated with neurological improvement in dogs with TL-IVDD, and that TNF-α may reflect phase- and method-dependent inflammatory responses after acupuncture treatment. Plasma IL-6, total plasma NAD(H) levels, and HIF-1α should be interpreted as exploratory biomarkers in this clinical setting.</p>