Reasoning for complexity is a fundamental competency in these complex times for solutions to social problems and decision-making. The purpose of this paper is to demonstrate the validity and reliability of the eComplexity instrument by presenting its psychometric properties. The instrument consists of a Likert-type scale questionnaire designed to measure college students' perceptions of their mastery levels of complex reasoning competency as well as the subcompetencies that comprise it. The instrument was applied to higher education students in different countries of Latin America and Spain. The questionnaire articulates four types of thinking: systemic, scientific, critical and innovative and consists of 25 items. The methodology used was instrumental and psychometric, which seeks to demonstrate the validity and reliability of the eComplexity questionnaire. The results obtained from the research were as follows: The exploratory factor analysis indicated a Kaiser-Meyer-Olkin index (KMO) > 0.80, a significance of p< 0.05 and a Cronbach's Alpha value of 0.93. Likewise, a Confirmatory Factor Analysis was carried out and was possible to corroborate the internal structure validity of the instrument. In addition to Cronbach's Alpha coefficient, McDonald's Omega, and Guttman's Lambda coefficients were calculated to calculate reliability. With the results obtained it was possible to conclude that the instrument is valid and reliable, can be used in various university contexts to support integrated training necessary to address current challenges and contribute to educational research. It is recommended for future studies that the research can be expanded by using an instrument that can move from perceptual terms to measuring levels of complex reasoning mastery, but it is valuable to contrast with the students' perception to have a broader vision.