This research article describes the design and application of an instrument for evaluating critical thinking from academic writing as a method to develop pedagogical reflection. This research was based on a quantitative methodology, with a descriptive scope, where 265 essays, written by Chilean pedagogy students, were analyzed. The ability to consistently and coherently relate arguments, and the ability to systematically articulate one’s point of view with other perspectives, were the greatest predictors in the development of a written text with a high level of critical thinking (Martin & White, 2003; Snow & Uccelli, 2009; Youngs & Bird, 2010).