This study explored healthcare professionals' perceived role in talking to adult patients about sharing their diagnosis with children. Semi-structured interviews were conducted to explore healthcare professionals' beliefs about how families could and should be supported when a parent has a serious illness. Participants were 24 healthcare professionals working in primary, secondary and tertiary NHS services in the UK with adult patients diagnosed with a serious illness. Data were analysed thematically. Many healthcare professionals reported systems to identify patients' family relationships, but this information was rarely used to initiate conversations on what and how to talk to children. It was frequently assumed that someone else in the healthcare system was supporting patients with family communication. Others reported there were more urgent priorities for the consultation or considered that talking to children was a private family matter. However, several professionals did undertake these conversations, viewing this as a central part of their role. Some healthcare professionals felt they had inadequate skills or confidence to raise talking to children with their patients and indicated a need for specific training to address this. The results highlight the importance of systematically documenting patients' relationships with children so that this information can be used to inform ongoing discussions with the healthcare team about what children have been told. Patients consistently report wanting support about how to talk to children and the benefits of effective communication are well documented. Dissemination of this evidence could encourage professionals across all specialities to include family-centred communication in routine patient care. Training resources are needed so that staff feel empowered and equipped to raise these sensitive subjects with their patients.