This cross-sectional study aimed to identify nursing diagnoses in critical patients at risk of developing pressure ulcer. It was carried out at an Intensive Care Unit in Fortaleza-CE, Brazil, using an intentional sample of thirteen subjects at risk of pressure ulcer, evaluated according to the Waterlow scale. In total, 45 nursing diagnoses were evidenced, seventeen of which were clinically significant for the development of pressure ulcer. The frequency levels for nine of these nursing diagnoses were ≥ 80%, mainly: Impaired skin integrity (100%), Impaired walking (87%), Impaired swallowing (80%), Impaired bed mobility (80%) and Impaired gas exchange (80%). The knowledge of those nursing diagnoses is important in detecting the effects and clinical basis of skin lesions.