Aim To explore nurses' experiences of supporting family caregivers in specialised home care while learning to use the Carer Support Needs Assessment Tool Intervention. Background The Carer Support Needs Assessment Tool Intervention can provide guidance for discussions with family caregivers in specialised home care concerning their specific support needs. Little attention has been paid to how nurses experience the use of the intervention in their everyday practice. Design This longitudinal study adopted an inductive qualitative approach using interpretive description. Methods Interviews were conducted at two time points. A total of 22 interviews took place with 12 nurses recruited from six specialised home care services. Data were analysed using interpretive description. Results Nurses' everyday clinical practice changed while learning to use the Carer Support Needs Assessment Tool Intervention, and they experienced professional and personal growth. Their supportive inputs shifted from being reactive towards being more proactive. Their approach changed from taking on great professional responsibility, towards a shared responsibility with family caregivers. The support altered from ad hoc contacts in the hallway, towards scheduled trustful conversations. Nurses were concerned about the amount of time and energy this kind of support might require. They pointed to the importance of holding good nursing skills to conduct this new way of having conversations. Conclusion Nurses' everyday clinical practice can be further developed through the use of the Carer Support Needs Assessment Tool Intervention. Nurses may develop both professionally and personally, increasing their ability to provide person-centred support. Relevance to Clinical Practice With the use of the Carer Support Needs Assessment Tool Intervention, nurses can create trusting conversations with family caregivers of patients with life-threatening illnesses cared for in specialised home care. Reporting Method Reporting of the study follows the Consolidated Criteria For Reporting Qualitative Research (COREQ) checklist (File S1). Patient or Public Contribution Participating nurses were involved in discussing the study design.