Background: The high support needs of persons with profound intellectual and multiple disabilities hamper their possibilities for self-determination. To support their self-determination understanding of what this means for this group is necessary. Method: A three-round Delphi procedure with international experts was undertaken to operationalise self-determination for persons with profound intellectual and multiple disabilities. The quantitative output of Likert scales guided us in finding consensus or differences in the qualitative data. First round qualitative data were analysed thematically. Results: The analysis revealed four topics: (1) statements regarding the characteristics of the person with profound intellectual and multiple disabilities, (2) statements regarding characteristics of the social environment, (3) statements regarding the concept of self-determination, and (4) statements regarding the definition and operationalisation of concepts. Conclusion: Consensus was found on the assumption that persons with profound intellectual and multiple disabilities can live a self-determined life and on the importance of the interplay between persons with profound intellectual and multiple disabilities and the environment in order to experience self-determination.