This study proposes the development of an instrument to measure complex thinking skills, which was applied to 256 university students to assess its psychometric properties and determine its validity on content, criterion, construct, and reliability. In this process, the instrument was submitted to the evaluation of a panel of experts, the conceptual model was verified through confirmatory factor analysis, and the criterion validity (convergent validity and discriminant validity) was determined in relation to other instruments. Finally, it is concluded that the results of the instrument validation process showed satisfactory statistical validity values. This allows establishing that the complex thinking assessment instrument (CTAI) is a psychometrically valid and reliable instrument to measure their cognitive abilities.