Background: Despite the progress made in recent decades on the phenomenon of futility in adult intensive care, recognizing it during clinical care practice remains a complex and sensitive process, during which questions are often raised for which concrete answers are difficult to find. Aims: To analyze the frequency with which futile nursing interventions are implemented in critically ill patients admitted to adult intensive care in specific situations and how often futile autonomous and interdependent nursing interventions are implemented in the same (...) population, as perceived by adult intensive care nurses. Research design: Cross-sectional, quantitative, and descriptive study, which employed a questionnaire constructed specifically for this research to assess the perception of therapeutic futility in nursing in adult intensive care. Following an evaluation of the psychometric properties, the questionnaire was made available in an electronic format on the EUSurvey platform between August and October 2024. The data was analyzed between November 2023 and March 2024 using the statistical software packages SPSS and R. Participants and research context: A simple random sample of nurses working in level II and level III intensive care units in Portugal. Ethical considerations: Research ethical approvals were obtained, and the participants provided informed consent. Findings/results: Four hundred and fourteen valid questionnaires were obtained. The results allow the identification of thirty-three statistically significant associations, the inference of intervals for the mean and median for the perception of futility of nursing interventions with a 95% confidence interval, and enable the hierarchization of nursing interventions implemented in critically ill patients admitted to adult intensive care units according to the nurses’ perception of their futility. Conclusion: There is a balance in nurses' perception of the futility of their interventions in the specific situations analyzed. There is statistically significant evidence that interdependent nursing interventions are, in general, more frequently perceived as futile when compared to autonomous nursing interventions. (shrink)