Interdisciplinary multimodal pain therapy (IMPT) is a biopsychosocial treatment approach for patients with chronic pain that comprises at least psychological and physiotherapeutic interventions. Core outcome sets (COSs) are currently developed in different medical fields to standardize and improve the selection of outcome domains, and measurement instruments in clinical trials, to make trial results meaningful, to pool trial results, and to allow indirect comparison between interventions. The objective of this study was to develop a COS of patient-relevant outcome domains for chronic pain in IMPT clinical trials. An international, multiprofessional panel (patient representatives [n = 5], physicians specialized in pain medicine [n = 5], physiotherapists [n = 5], clinical psychologists [n = 5], and methodological researchers [n = 5]) was recruited for a 3-stage consensus study, which consisted of a mixed-method approach comprising an exploratory systematic review, a preparing online survey to identify important outcome domains, a face-to-face consensus meeting to agree on COS domains, and a second online survey (Delphi) establishing agreement on definitions for the domains included. The panel agreed on the following 8 domains to be included into the COS for IMPT: pain intensity, pain frequency, physical activity, emotional wellbeing, satisfaction with social roles and activities, productivity (paid and unpaid, at home and at work, inclusive presentism and absenteeism), health-related quality of life, and patient's perception of treatment goal achievement. The complexity of chronic pain in a biopsychosocial context is reflected in the current recommendation and includes physical, mental, and social outcomes. In a subsequent step, measurement instruments will be identified via systematic reviews.