Purpose: This multi-center mixed methods study aims (1) to evaluate the efficacy of the adapted German PRO-SELF© Plus PCP, designed to improve outpatients' and their family caregivers' (FCs) management of pain on pain intensity; (2) to explore the intervention's effect on associated symptoms and other patient and FC outcomes; (3) to explore patients' and FCs' experiences with cancer pain management in both the intervention group and the usual care group; and (4) to interpret quantitative and qualitative findings and eventually synthesize them. To our knowledge, this will be the first evaluation of an intervention to support pain self-management in German speaking outpatients with cancer related pain and their FCs.