The intensive care unit (ICU) syndrome includes a series of psychological abnormalities and cognitive impairments observed in some ICU patients. Nurses often fail to recognize a patient's symptoms until they become visibly agitated and confused. Till date, the ICU syndrome has not been conceptually analyzed. This article utilized the method of concept analysis described by Walker and Avant (2019). By integrating the relevant literature, we defined the critical attributes of the ICU syndrome and constructed the cases, including model, borderline, contrary, and related cases, to elucidate the concept. The antecedents and consequences of the ICU syndrome, measurement tools, and clinical practice applications were also substantiated. This analysis is expected to enhance the ICU nurses' ability to treat and prevent ICU syndromes among ICU patients and improve the quality of critical care.