The number of one-to-one mobile programs in elementary schools as a resource to substitute the textbook has become popular worldwide. However, findings of studies that seek to enable understanding of how the daily use of these mobile devices affects student's engagement in the classroom are heterogeneous. The authors utilized and adapted a self-system model of motivational development in order to better understand the mechanisms behind the promotion of academic engagement in one-to-one iPad programs. For this, an analysis using structural equations was conducted on data collected from a network of 20 elementary schools and 1,011 5th and 6th grade students in Spain, who used iPads daily in their Language and Mathematics courses. The results showed that certain activities--according to the course--with the iPad influenced the students' engagement, while promoting authentic learning and satisfying their needs. The study contributes with a comprehensive approach and knowledge about the reasons behind the success or failure of these types of programs on learner engagement.