Background: Primary care systems are challenged by demographic, social, and technological evolutions. Changing care needs due to an aging population, increasing noncommunicable diseases, and multimorbidity affect the service capacity and quality of care. These complex care questions increase the need for interdisciplinary collaboration. Within the general practice (GP), the collaboration between general practitioners and nurses is rising. Research shows that 80% of the Belgian practices that already employ a nurse are convinced of the added value of the collaboration. Moreover, nurses provide cost-effective and high-quality chronic care with high patient satisfaction. The position of a nurse in a GP is still rare in Flanders. The integration of nurses in primary healthcare is challenging. Aim: The aim of this research project was to (1) identify barriers and facilitators of integrating nurses in GPs in Flanders, and to (2) co-design a nurse-led method supporting the collaboration within GPs in Flanders. Method: A two-phase participatory action research design was implemented. The first phase identifying barriers and facilitators, consisted of a literature review, interviews with stakeholders (n=12), non-participating observations of conversations between nurses and general practitioners at the start of their collaboration (n=11), and 2 focus group discussions with nurses and general practitioners. The second, co-design, phase consisted of semi-structured interviews with practice nurses (n=9) and a co-creative focus group session with nurses (n=5). An advisory committee of experts in the field of GP, nursing, primary care, education, and research guided the research process. Results: The first phase identified five important topics and the decision-making process of the collaboration with a nurse: (1) pre-employment needs assessment of the GP, (2) match between nurses and general practitioners, (3) employment status of nurses, (4) onboarding process, and (5) optimalisation towards complementary collaboration. ...