Objective: The goal of the current study was to examine the association of pain beliefs and pain-related outcomes, such as pain interference, physical functioning, depression, and anxiety. The impact of a literacy-adapted psychosocial treatment on the modification of pain beliefs was also explored. Background: Previous research has shown an association between pain beliefs and pain-related outcomes. To date, most studies have found a positive relationship between biomedical pain beliefs and poor psychological and physical outcomes. There is also some evidence to suggest that pain beliefs are a unique predictor for pain outcomes, above and beyond the influence of demographic characteristics. Pain beliefs can be modified through psychosocial treatments for chronic pain, such as Cognitive Behavioral Therapy (CBT). There is a paucity of research examining the biomedical or biopsychosocial pain beliefs of a low-SES population, or whether a psychosocial intervention is effective at changing biomedical or biopsychosocial pain beliefs among this understudied patient population. Method: 290 participants from the Learning About My Pain (LAMP) Study completed questionnaires before starting a 10-week literacy-adapted psychosocial treatment for chronic pain. Participants were randomly assigned to group cognitive-behavioral therapy (CBT), group pain education (EDU) or medical treatment-as-usual (UC). Participants also completed questionnaires at post-treatment. Results: There was a significant positive and weak association between pain beliefs and pain-related outcomes. Regression results revealed that biomedical pain beliefs had a stronger association with physical functioning, while biopsychosocial pain beliefs had a stronger association with psychological functioning. Patient’s biomedical pain beliefs decreased and biopsychosocial pain beliefs increased following participation in a literacy-adapted psychosocial intervention. Conclusions: The findings in this study suggest that certain specific pain beliefs may be more related to particular aspects of physical and psychological functioning. These findings also provide further support for the benefits of literacy-adapted psychosocial treatments and highlight the benefits of providing treatments consistent with a biopsychosocial model of pain. Overall, the results of this study demonstrate the importance of pain belief assessment among an understudied population and its implications to improve our understanding of patient’s pain conceptualization and how it relates to patient outcomes.