Background: In this study, we analyse the process of academic reading demotivation in elementary preservice teachers. Academic reading motivation is conceptualised from the Expectancy-Value Theory, with the respective eponymous dimensions as well as interest, attainment, utility, and cost as subcomponents for task value. Methods: These motivational variables were measured by the Escala Motivacional por la Lectura Académica (Academic Reading Motivation Scale). Analysis focused on confirming the demotivation process organised by four different educational motivation profile types (clusters), as well as by cohorts. Participants were a total of 785 elementary preservice teachers from seven Chilean universities, both public and private, from six regions of Chile, enrolled in the first, third and last years of their programme. This population was tested, with a subsample (n = 295) retested the following year. Results: Results show a concentration of negative motivational changes in the “school motivation” group, as well as changes during the first years of the programme. The more affected dimensions are utility and cost. There is no evidence for changes in feeling of competence for academic reading (expectancy). Conclusions: We conclude the importance of focusing efforts on avoiding these negative motivational changes in students that demonstrate three key characteristics: they want to become primary teachers, they are engaged in their studies, and finally, they want to work in the school system.