IntroductionIn recent years, medical treatment for cancer has improved, thereby increasing the life expectancy of patients with cancer. Hence, the focus in healthcare shifted towards analysing treatments that offer to decrease distress and improve the quality of life of patients with cancer. The psychological burden of patients with cancer originates from all kinds of psychosocial challenges related to diagnosis and treatment. Cancer counselling centres (CCounCs) try to address these concerns. However, the current literature lacks research on the effectiveness of CCounCs. This study aims to assess the effectiveness of CCounCs with regard to distress and other relevant psychosocial variables (quality of life, anxietyand so on).Methods and analysisThis prospective observational study with a non-randomised control group has three measurement points: before the first counselling session (baseline, t0) and at 2 weeks and 3 months after baseline (t1, t2). Patients and their relatives who seek counselling between December 2018 and November 2020 and have sufficient German language skills will be included. The control group will be recruited at clinics and oncological outpatient centres in Hamburg. Propensity scoring will be applied to adjust for differences between the control and intervention groups at baseline. Sociodemographic data, medical data and counselling concerns are measured at baseline. Distress (distress thermometer), quality of life (Short Form-8 Health Survey, European Organization for Research and Treatment of Cancer Core Quality of Life Questionnaire-Core 30), anxiety (Generalized AnxietyDisorder-7), depression (Patient HealthQuestionnaire-9) and further psychosocial variables are assessed at all time points. With a total of 787 participants, differences between the intervention and control groups of a small effect size (f=0.10) can be detected with a power of 80%.Ethics and disseminationThe study was registered prior to data collection with the German Registration of Clinical Trials in September 2018. Ethical approval was received by the local psychological ethical committee of the Center for Psychosocial Medicine at the University Medical Centre Hamburg-Eppendorf in August 2018. The results will be published in peer-reviewed journals.Trial registration numberDRKS00015516; Pre-results.