Introduction/Background: Carers play a crucial role in supporting patients with serious illnesses, yet their own support needs often remain unmet. The Carer Support Needs Assessment Tool (CSNAT-I) is an evidence-based, person-centred assessment tool designed to identify and address the needs of carers supporting critically ill patients. Aim: This study explores the perspectives of nurses and informal carers regarding the implementation and use of CSNAT-I in palliative cancer care. Method: Semi-structured interviews were conducted with three oncology nurses (via telephone with detailed field notes) and one focus group with four palliative care nurses, alongside five carer interviews. All interviews were audio recorded and transcribed verbatim. Data were analysed using content analysis. Results: Although nurses acknowledged the importance of supporting carers, the integration of CSNAT-I was hindered by time constraints, unclear implementation processes, and limited understanding of its purpose. Both nurses and carers preferred ongoing dialogue and relational continuity over structured assessments. The CSNAT-I was often perceived as a conversation starter rather than a tool to guide support systematically. While some carers received practical help after the assessment conversation, they did not necessarily associate this support with the CSNAT-I. Conclusion with implication for practice (educational and/or clinical): The study highlights key challenges with the CSNAT-I, such as issues related to timing, workload pressures, and limited awareness of its intended purpose. Carers emphasised the importance of continuous support and consistent contact points with healthcare professionals rather than relying solely on structured assessments. While CSNAT-I appears to play a valuable role in legitimising time spent with carers, its full potential is likely to be realised better if it is embedded within person-centred pathways that include clear strategies for implementation and follow-up.