Background and aim: A complex healthcare environment, with greater need for care based on the patient and evidence-based practice, are factors that have contributed to the increased need for critical thinking in professional competence. At the theoretical level, Alfaro-LeFevre () put forward a model of critical thinking made up of four components. And although these explain the construct, instruments for their empirical measurement are lacking. The purpose of the study was to develop and validate the psychometric properties of an instrument, the Nursing Critical Thinking in Clinical Practice Questionnaire (N-CT-4 Practice), designed to evaluate the critical thinking abilities of nurses in the clinical setting. Methods: A cross-sectional survey design was used. A pool of items was generated for evaluation by a panel of experts who considered their validity for the new instrument, which was finally made up of 109 items. Following this, validation was carried out using a sample of 339 nurses at a hospital in Barcelona, Spain. Reliability was determined by means of internal consistency and test-retest stability over time, although the validity of the construct was assessed by means of confirmatory factor analysis. Results: The content validity index of the N-CT-4 Practice was .85. Cronbach's alpha coefficient for the whole instrument was .96. The intraclass correlation coefficient was .77. Confirmatory factor analysis showed that the instrument was in line with the four-dimensional model proposed by Alfaro-LeFevre (2016). Linking evidence to action: The psychometric properties of theN-CT-4 Practice uphold its potential for use in measuring critical thinking and in future research related with the examination of critical thinking.