PurposeThis study aimed to establish the content validity of the proposed nursing diagnosis (ND) “Adult Disuse Syndrome” and all its components.MethodThis is an exploratory descriptive study of diagnostic content validation under Fehring's proposal. Forty three expert nurses with clinical, teaching, and research experience analyzed the components of the diagnosis. The representativeness and relevance of the components of the diagnosis under study were evaluated through a Likert‐type questionnaire. Data distribution analysis was carried out, and the components were validated if their content validity index (CVI) was over 0.80. The overall CVI was obtained for the clinical indicators.FindingsA total of 12 defining characteristics (DCs) were validated, 3 etiological factors were highly related, 6 risk populations were confirmed, and 11 conditions were considered associated. Most validated DCs refer to the physical dimension, but those focusing on the psychological and social dimensions were also validated. The etiological factors were related to the effects of immobility. The risk populations were validated in different contexts or situations, and associated conditions were mainly oriented toward chronic conditions.ConclusionsThis study validated the content of the elements of the proposed ND “Adult Disuse Syndrome.” These were considered relevant and appropriate by both academic and clinical experts.Implications for nursing practiceThe content validation by experts of the components of the ND “Adult Disuse Syndrome” provides nurses with a tool for the identification of the phenomenon that exceeds the risk and occurs frequently in patients exposed to the effects of immobility. At the same time, it will guide the results pursued in the care plan and the application of the respective nursing and interdisciplinary interventions that favor the reduction of the complications derived from disuse.