This is a secondary data analysis of a subgroup of participants who received the Learning About My Pain (LAMP) intervention (clinicaltrials.gov identifier NCT01967342). We examined the effects of LAMP on pre-to-post changes in biomedical and biopsychosocial pain conceptualization and whether those changes in pain conceptualization were associated with physical and psychological functioning. Participants were randomized into three conditions: Cognitive Behavioral Therapy (CBT), Pain Psychoeducation (EDU), or Usual Medical Care (UC). Results based on 225 participants who completed the Pain Concepts Questionnaire (PCQ) showed a pre-to-post reduction in biomedical pain conceptualization (BM), an increase in biopsychosocial pain conceptualization (BPS), and an increase in BPS/BM ratio for CBT and EDU but not UC. There were no differences between CBT and EDU in post-treatment PCQ scores. Compared to those with lower BM pain beliefs scores at post-treatment, participants endorsing higher BM pain beliefs scores reported greater pain intensity and greater pain interference. Furthermore, higher BM pain beliefs scores at post-treatment and lower BPS/BM ratio were associated with higher levels of pain catastrophizing. Overall, results of this study suggest the need for targeting specific pain beliefs that influence pain-related outcomes. Perspective: This article presents the potential benefits of providing literacy-adapted psychosocial treatments to expand pain conceptualization beyond a biomedical-only understanding and toward a biopsychosocial conceptualization of the experience of pain. Furthermore, the association of changes in pain conceptualization and pain-related functioning argues for its potential clinical relevance.