Background:Dental caries comprises the most prevalent chronic disease in children worldwide and is considered a public health problem.Introduction:Few educational oral health applications, directed to the preschool public, are available. The present study aimed at developing an educational game in application format for mobile devices and tested its usability.Materials and Methods:Forty-three children were randomly selected to participate in the study. The methodology used in the development of the application was based on an interactive children's book flux design. The application was elaborated for the Android™ and iOS™ platforms. To evaluate usability, a test method composed of observation and interview surveying was used, and the measuring mechanism consisted of the User's Success Rate. The sample (N = 43) was randomly composed of preschool students (3-5 years of age) from a public school in Brazil.Results:In the effectiveness tests, the success rates of the Story and Game Menus were 97.6% and 85.3%, respectively. In the efficiency tests, the respective rates were 80.2% and 82.1%. The satisfaction evaluation rate was 99.7%.Discussion:The game "Put the healthy food into the mouth" showed to be difficult in utilization due to the children's lack of knowledge concerning healthy foods (p < 0.001 and 95% confidence interval). Three year olds demonstrated a greater requirement for assistance during navigation.Conclusions:The application was successful regarding the following three assessed attributes: (1) effectiveness, (2) efficiency, and (3) satisfaction. However, dietary education was observed to be necessary for the children and their guardians.