The increased use of smartphones and tablets sets the stage for new mobile-based educational programs that seek to increase student learning and engagement in school and at home. This study examines the effectiveness of Escribo Play, a game-enhanced educational program, on preschool students' phonological awareness, word reading, and writing skills. The randomized controlled trial was conducted with 749 students from 62 classrooms from 17 schools located in five cities. Quantitative pretesting and posttesting procedures using standardized instruments were employed. The results indicate that the experimental classrooms that used the 20 games for 3 months gained 68% in their reading scores compared to control classrooms (d = 0.40). They also gained 48% more in writing scores (d = 0.20). Multilevel analysis indicated that these findings were statistically significant.