Introduction Effective doctor-patient communication in oncology settings can be challenging due to the complexity of the cancer disease trajectory. The challenges can become greater when doctors and patients do not share a common language and need to rely on language mediators. The aim of this study is to provide evidence-based recommendations for healthcare professionals, patients and language mediators on how to interact with each other during language-mediated consultations in oncology settings. Methods and analysis A systematic review of the literature on communication problems in monolingual and multilingual oncology settings will be conducted. Thirty language-mediated consultations with Turkish-speaking or Arabic-speaking cancer patients, language mediators and Dutch-speaking oncologists/haematologists will be video-recorded in three urban hospitals in Flanders, Belgium. All participants will be interviewed immediately after the consultation and 2 weeks after it by means of video-stimulated recall. Multimodal interaction analysis will be combined with qualitative content analysis to allow for the identification of communication practices when communication problems occur. Ethics and dissemination The study has been approved by the following ethics committees: Ghent University Hospital, Antwerp University Hospital, Antwerp Hospitals Network (ZNA). Results will be published via (inter)national peer-reviewed journals and the findings of the study will be communicated using a comprehensive dissemination strategy aimed at healthcare professionals, patients and language mediators.