Background <p>The global shortage of nurses places additional pressure on healthcare systems and nursing education. Effective mentoring is crucial for students, and various interventions have been developed to enhance the mentoring competences of nurses working with undergraduate nursing students. However, research on mentoring competences in the context of post-registration critical care nursing remains limited.</p> Methods <p>This study aimed to develop an educational intervention to enhance the critical care nurses’ mentoring competence. We employed a qualitative design, guided by the UK Medical Research Council’s framework for complex interventions and the European guideline on clinical nurse mentor’s mentoring competence development. We conducted three focus group interviews with 11 critical care nurses from university and local hospitals in Northern Norway and used reflexive thematic analysis to analyse the data.</p> Results <p>We identified four themes essential for the intervention: mentoring as its own skillset, mentoring as an act of power, mentoring as a collaborative effort, and organisational support for mentoring. Participants emphasised the need for practical tools to address challenges such as diverse student learning needs, fostering reflection, and managing power dynamics. They also highlighted the importance of shared understanding of mentoring practices within the units and robust organisational support, including time allocation for both daily mentoring and competence development, and leadership commitment.</p> Conclusions <p>The findings informed the development of a blended learning educational intervention combining online learning with in-person simulated discussions. The intervention focuses on practical tools, simulations, and fostering a supportive mentoring environment tailored for critical care nursing context.</p>