Objective: A key issue in chronic pain treatment concerns the changes necessary for improved physical and emotional functioning. Traditionally, reducing pain intensity and pain-related distress have been viewed as a prerequisite for these improvements. Alternatively, acceptance and commitment therapy, a behavior change approach, theorizes that pain and distress reduction are not necessary for improvement, rather responses must change, such that functioning improves in clearly specified areas (e.g., engagement in valued activities, decreased disability in social activity) even when pain and distress persist. Method: This study sought to directly examine aspects of change in pain and distress over the course of an interdisciplinary program of acceptance and commitment therapy in relation to functioning at treatment’s conclusion and a 3-month follow-up in 174 treated patients. Latent change trajectories of pain intensity and pain-related distress were assessed weekly over 4 weeks of treatment and analyzed via latent growth curve and growth mixture modeling. Results: A single latent trajectory with a decreasing quadratic slope was indicated for pain, while 2 separate trajectories were identified for pain-related distress 1 of linear decrease and the other an early increase followed by a decrease to initial level. Overall, and with only 3 exceptions across multiple tests, results indicated that trajectories of pain and distress during treatment were not significantly associated with improvements in functioning at treatment’s conclusion and follow-up. Conclusions: This pattern of findings suggests that significant improvements in functioning may not require decreases in pain intensity and pain-related distress during treatment for chronic pain.