BackgroundThe prevention of unplanned endotracheal extubation (UEE) is significant for the critical care of intensive care unit (ICU) patients.AimTo develop a questionnaire to assess the knowledge, attitude, and practice (KAP) of the nurses regarding of the prevention of UEE in ICU patients with transoral endotracheal intubation (TEI) and to test the validity and reliability of the questionnaire.Study DesignItems relevant to KAP were prepared following a literature review, and then screened using a Delphi expert consultation, pre‐test, and factor analysis. The nursing staffs in four tertiary hospitals in Qinghai, Jiangsu, Gansu, and Shandong provinces were surveyed to test the reliability and validity of the questionnaire.ResultsThe questionnaire contained 76 items, including 10, 37, and 29 in the dimensions of knowledge, attitude, and practice, respectively. The scale‐level content validity index (S‐CVI) of the questionnaire was 0.96. The results of exploratory factor analysis (EFA) showed that the Kaiser–Meyer–Olkin value was 0.956, indicating that the sample was adequate and suitable for factor analysis. The result of the Bartlett spherical test was significant (p < .001), indicating that the questionnaire was suitable for further EFA. A total of six common factors were extracted by EFA with a cumulative variance interpretation rate of 85.52%, indicating that the questionnaire had good structural validity. The Cronbach's alpha was 0.981 for the whole questionnaire; and was 0.966, 0.996, and 0.981 for the dimensions of knowledge, attitude, and practice, respectively. The test–retest reliability for the questionnaire was 0.843.ConclusionsThe developed questionnaire has good reliability and validity and can be used as a scientific tool for the nursing leaders to prevent UEE in ICU patients with TEI.Relevance to Clinical PracticeThe instrument provides a theoretical reference for establishing preventive strategies and management programs in clinical practice.