Purpose: To explore content validity of the ICF core set for Diabetes Mellitus from nurses’ perspective. Materials and methods: A two-round Delphi study was conducted with nurses specialized in diabetes care, who were recruited by purposive sampling. Level of agreement on relevance of ICF categories was calculated using Item-level Content Validity Index. Results: Twenty-seven nurses judged 147 second-level ICF categories on relevance for people with Diabetes Mellitus. Agreement was reached on 65 (44.2%) categories, of which 46 were from the ICF core set for Diabetes Mellitus, 17 were from previous validation studies, and two were additional categories that were mentioned as relevant. Forty-six out of the 65 categories were derived from the component body functions and structures. No agreement was reached on 82 (55.8%) categories, of which 33 were derived from the component environmental factors. Conclusions: Content validity of the ICF core set for Diabetes Mellitus was partially supported by specialized nurses. Agreement was predominantly reached on biomedical categories. Content validity of categories derived from environmental factors received little support. Relevance: The nursing profession should be aware of a gap between the current biomedical focus and the desired biopsychosocial approach; the latter of which is recommended in chronic care.IMPLICATIONS FOR REHABILITATION The International Classification of Functioning, Disability and Health (ICF) encourages a biopsychosocial approach in health care, and ICF core sets, such as the core set for Diabetes Mellitus, are useful in identifying the needs of patients. Content validity of the ICF core set for Diabetes Mellitus was partially supported by nurses specialized in diabetes care; agreement was predominantly reached on biomedical categories. The nursing profession should be aware of a potential gap between the current biomedical focus and a desired biopsychosocial approach, which is particularly recommended in chronic care. It is recommended that nurses take part in future revisions of ICF core sets; a multidisciplinary approach enables members to learn from each other’s perspectives, including from those of patients.