Background: General practitioners (GPs) are well-positioned to enhance shared decision-making (SDM) about treatment for patients with advanced cancer. However, to date, little is known about GPs’ views on their contribution to SDM. Aim: To explore GPs’ perspectives on their role in SDM about palliative cancer treatment and the preconditions to fulfil this role. Design and setting: Qualitative interview study among Dutch GPs. Method: GPs were sampled purposefully and conveniently. In-depth semi-structured interviews were conducted, recorded and transcribed verbatim. The transcripts were analysed by thematic analysis. Results: Most GPs reported practices that potentially support SDM: checking the quality of a decision, complementing SDM and enabling SDM. Even though most GPs felt that decision-making about systemic cancer treatment is primarily the oncologist’s responsibility, they do recognise their added value in the SDM-process because of their gatekeeper position, the additional opportunity they offer patients to discuss treatment decisions and their knowledge and experience as primary healthcare provider at the end of life. Preconditions for supporting the SDM-process were 1) good collaboration with oncologists, 2) sufficient information about the disease and its treatment, 3) sufficient time, 4) a trusting relationship with patients and 5) patient-centred communication. Conclusion: GPs may support SDM by checking the quality of a decision and by complementing and enabling the SDM-process to reach high quality decisions. This conceptualisation may help understand how SDM is carried out through interprofessional collaboration and provide tools for how to adopt a role in the interprofessional SDM-process.