Abstract: Introduction: Providing effective treatment for debilitating chronic pain is a challenge among many populations including military service members. Cognitive behavioral therapy for chronic pain (CBT-CP) is a leading psychological pain treatment. Pain catastrophizing is a pivotal mediator of pain-related outcomes. The purpose of this study was (1) to identify patient subgroups who differ in response to CBT-CP and (2) to explore the characteristics that define these patient subgroups. The overall goal was to obtain a better understanding of factors that may influence response to CBT-CP. Materials and methods: This study was a secondary analysis of data from a clinical trial of 149 U.S. active duty service members with chronic pain. Participants underwent group-based CBT-CP for 6 weeks and completed pre- and posttreatment assessments. Finite mixture models were employed to identify subgroups in treatment response, with pain impact score as the primary outcome measure. Results: We identified two classes of nearly equal size with distinct pain impact responses. One class reported improved pain impact scores following CBT-CP. This improvement was significantly associated with lower (better) baseline depression scores and greater improvement in posttreatment pain catastrophizing. In contrast, the other class reported slightly worse mean pain impact scores following CBT-CP treatment; this response was not related to baseline depression or change in pain catastrophizing. Conclusions: Our findings demonstrate that a sizable proportion of individuals with chronic pain may not respond to group-based CBT-CP and may require a more individualized treatment approach.