To determine the correlation between posttreatment trunk range of motion (ROM) and isometric strength (TIS) and pain and disability in patients who underwent multimodal rehabilitation for low back pain (LBP).  In this prospective cohort study, 122 patients undergoing multimodal rehabilitation for LBP were analyzed. The pre- and posttreatment numerical pain rating scale (NPRS) and the Oswestry disability index (ODI) scores, as well as trunk ROM and TIS were compared. The Pearson correlation was used to determine correlation between posttreatment clinical outcomes and ROM and TIS.  At the end of treatment, the mean NPRS (  < 0.0001) and ODI (  < 0.0001) scores, mean trunk extension (  < 0.0001), and flexion (  < 0.0001) ROMs improved significantly. Similarly, posttreatment, the mean extension (  < 0.0001) and flexion (  < 0.0001) TISs improved significantly. There was a weak correlation between the NPRS score and ROM extension (r = -0.24,  = 0.006) and flexion strength (r = -0.28,  = 0.001), as well as between the ODI score and TIS extension (r = -0.30,  = 0.0007) and flexion (r = -0.28,  = 0.001).  Despite significant improvement in pain, disability, trunk ROM, and TIS with multimodal treatment, there was a weak correlation between posttreatment pain and function and trunk ROM and TIS. Improvement in pain and function with physical rehabilitation treatment for LBP is a complex phenomenon and needs further investigation.