Background/Objectives: Chronic non-cancer pain often requires approaches beyond pharmacological treatment. This protocol describes a mixed-methods study evaluating the effectiveness of a multicomponent intervention based on non-pharmacological therapies (NPhTs) and exploring participants’ post-intervention experience. Methods: The design includes a randomized, controlled, two-arm parallel-group clinical trial with 1:1 allocation, embedded within a mixed-methods approach that includes a qualitative phenomenological strand. This study will be conducted at Hospital San Juan de Dios del Aljarafe, Spain. A total of 160 adults with chronic non-cancer pain will be randomly assigned to the intervention or control group. The intervention group will receive five weekly 3.5 h face-to-face sessions combining pain education, emotional regulation, cognitive-motivational and mind–body techniques, lifestyle recommendations, peer support, and home practice, supported by a mobile application. The control group will continue usual care, without the workshop or intervention-related app content. The primary outcome will be change in the EuroQol-5D (EQ-5D) index from baseline to 1 month. Secondary outcomes will include the EQ-5D visual analogue scale (VAS) score, pain intensity, well-being, self-esteem, resilience, anxiety and depression, pain catastrophizing, medication use, and healthcare resource use. Outcomes will also be assessed at 4 months and, in the intervention group, at 7 months. Semi-structured interviews will explore the participants’ experiences, perceived usefulness of the techniques, and barriers and facilitators to maintaining the strategies learned. Conclusions: This protocol will evaluate the effectiveness and acceptability of a structured group-based NPhT intervention for chronic non-cancer pain. The findings may inform its applicability to person-centered and self-care-oriented models of care. Trial registration: ClinicalTrials.gov NCT06440668.