Family strongly influences student health behavior. However, alcohol-preventive education programs that link parents and school for intermediate-elementary school students remain scarce. Although online educational programs constitute effective interventions to intentionally improve health behaviors, traditional methods are used to implement alcohol- prevention programs for students. In this study, we aimed to (1) develop an online school-child-family alcohol-prevention program based on the theory of planned behavior and (2) examine the preliminary effects of the program on intention to consume alcohol among intermediate-elementary school students. This single-group, pre- and posttest study enrolled 46 Grade 3 students from a public elementary school in a metropolitan South Korea city and ascertained the preliminary effects of a 5-week online alcohol-prevention program by using the alcohol drinking prevention behavior scale. Attitudes, perceived behavioral control, and intention of alcohol-preventive behaviors significantly improved (p < .05) whereas subjective norms did not. The online alcohol-prevention program based on the theory of planned behavior and school-child-family linkage beneficially influenced intention, attitude, and perceived behavioral control for alcohol-prevention behavior, and the effectiveness and convenience of this program underscores its potential application as an educational intervention to improve health behaviors of intermediate-elementary school students.