Background: Up to 64% of cancer patients experience pain, and as many as 40% of patients with pain do not receive adequate pain management. And while potential to reduce pain has been shown in several interventions that support patients' self-management, effects have been moderate. Purpose: This multicenter mixed methods study primarily aims to evaluate the efficacy of the adapted German PRO-SELF© Plus Pain Control Program (PCP) on pain intensity, to explore the intervention's effect on associated symptoms and other patient and family caregiver (FC) outcomes, and to explore patients' and FCs' experiences with cancer pain management.