Background <p>Nursing care models that incorporate a skill mix, including care assistants, are increasingly introduced in intensive care units (ICUs) to address workforce challenges. Understanding staff experiences with the early implementation of such models is essential to support effective collaboration and safe care delivery. This study aimed to explore the ICU nurses’ and care assistants’ experiences with a newly implemented skill mix, focusing on collaboration, role allocation, and perceptions of care delivery.</p> Methods <p>An exploratory qualitative study was conducted using four focus group meetings with 33 ICU nurses and nine care assistants working in two adult ICUs of a large tertiary hospital in the Netherlands (August to December 2023). Data were audiotape-recorded, transcribed verbatim, independently coded by two researchers, and analysed using thematic content analysis.</p> Findings <p>Three major themes were identified: (1) <i>Navigating change and adopting roles</i>, including clear and continuous communication, realistic expectations, and guidance through team managers; (2) <i>Collaboration and team dynamics</i>, encompassing team spirit, recognition to bridge a knowledge gap, opportunities for professional growth, and added value in essential care; (3) <i>Balancing responsibilities in delivering safe care</i>, highlighting tensions related to task allocation and accountability during early implementation.</p> Conclusion <p>The findings of this early phase evaluation illustrate tensions experienced by ICU nurses and care assistants when adapting to new role distributions within a nursing care model including skill mix. Clear and continuous communication, aligned expectations, and practical support tools—such as guidelines or task cards—facilitate collaboration and support ICU teams during the implementation of such models.</p> Trial registration <p>Not applicable.</p>