This study examines Patient-Reported Outcome Measurement Information System (PROMIS®)-29 v1.0 outcomes of chiropractic care in a multi-site, pragmatic clinical trial and compares the PROMIS measures to: 1) worst pain intensity from a numerical pain rating 0-10 scale, 2) 24-item Roland-Morris Disability Questionnaire (RMDQ); and 3) global improvement (modified visual analog scale). A pragmatic, prospective, multisite, parallel-group comparative effectiveness clinical trial comparing usual medical care (UMC) with UMC plus chiropractic care (UMC+CC). 3 military treatment facilities. 750 active-duty military personnel with low back pain. Linear mixed effects regression models estimated the treatment group differences. Coefficient of repeatability to estimate significant individual change. We found statistically significant mean group differences favoring UMC+CC for all PROMIS®-29 scales and the RMDQ score. Area under the curve estimates for global improvement for the PROMIS®-29 scales and the RMDQ, ranged from 0.79 to 0.83. Findings from this pre-planned secondary analysis demonstrate that chiropractic care impacts health-related quality of life beyond pain and pain-related disability. Further, comparable findings were found between the 24-item RMDQ and the PROMIS®-29 v1.0 briefer scales.