INTRODUCTION: Cancer affects not only patients but also their families, increasing the risk of stress-related illnesses among family members. Despite the development of various support interventions, family members continue to report unmet support needs, largely due to the limited implementation of these interventions into routine care or their lack of relevance to family needs. Co-design approaches, which involve stakeholders in the development process, are recommended to enhance both implementation and relevance. This scoping review aims to map the available evidence on co-design approaches in family interventions within oncology, examining key themes, methodologies and outcomes of interventions.

METHODS AND ANALYSIS: This scoping review will be conducted in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analysis extension for Scoping Reviews checklist and the Joanna Briggs Institute framework. The review will follow five stages: identifying the research questions, retrieving relevant studies, selecting studies, charting data and collating, summarising and reporting the results. The research will focus on co-design approaches in family interventions in oncology, exploring activities involved, barriers encountered and their impact on outcomes. A comprehensive search was conducted in EMBASE, MEDLINE, Scopus, CINAHL and PsycINFO databases in August 2024, with no date restrictions, and articles will be selected based on predefined inclusion criteria. Study selection will be performed independently by two reviewers, with disagreements resolved by a third. All reviewers will carry out the data extraction. Data will be analysed using descriptive content analysis and presented through narrative summaries, tables and diagrams to highlight study characteristics and research aims. The findings will inform future research and practice, offering insights into co-design strategies in family interventions in oncology.

ETHICS AND DISSEMINATION: Ethical approval is not needed as this scoping review does not involve collecting data from human participants. The results produced from this review will be submitted to a scientific peer-reviewed journal for publication and will be presented at scientific meetings. TRIAL REGISTRATION DETAILS: https://doi.org/10.17605/OSF.IO/2RWB9.