With inclusive research being an emerging field of interest, there is growing recognition that establishing collaborative relationships between researchers with and without ID entails specific demands. However, since studies on collaboration in inclusive research merely provide individual reports on experiences and challenges in one particular research project, building a shared knowledge base of concrete competencies considered important for those involved merits attention. This study contributes to a shared knowledge base in asking people with and without ID with (experiential) knowledge of inclusive research for competencies they consider important in collaborating in inclusive research in general, that is, without reference to a specific research project they participated in. Researchers with and without ID, coaches, policy makers, and teachers involved in the education of people with ID participated in this study. Data were collected from a focus group, individual interviews, and expert meetings. Qualitative analysis was carried out immediately after each moment of data collection, providing the use of increasing insights in each consecutive phase of data collection. Participants describe that establishing collaborative relationships between researchers with and without ID in inclusive research requires the commitment of both parties. They mentioned concrete competencies they consider important for people with and without ID to collaborate in inclusive research in the categories: building a mutual relationship, communicating, achieving a collaboration in which everyone involved can contribute, being aware of skills and developmental needs, and being aware of impact. Clearly, describing competencies for people with and without ID is not intended to exclude anyone who does not possess these competencies from collaboration in inclusive research. However to avoid “tokenism,” this study might contribute to effective participation of people with ID in inclusive research in providing concrete competencies considered important in collaboration.