Parental experience of initiation of alcohol drinking has been identified as one of the early causes of alcohol drinking in preadolescents in many countries, including Japan. This study identified the association between parental alcohol-related knowledge and the initiation of alcohol use among preadolescent students in an urban area in Japan. Self-administrated questionnaires were distributed to 420 parents of kindergarteners and elementary school students, of which 339 were filled and returned (response rate: 81%). The parents’ experience in initiating alcohol drinking in their children and their knowledge about the effects of alcohol on youth were explored. The requirements for drinking prevention programs for youth were also investigated. The result showed that a significantly higher proportion of parents of elementary school students had experiences of initiating alcohol use in their children compared to parents of kindergarten children. The parents’ knowledge regarding the effects of alcohol on youth showed no significant difference between the two parent groups. These data indicate that the age of children is the only factor as opposed to parents’ knowledge. We also found significant differences in the requirements of prevention programs between the two parent groups. The results of this study can contribute to the design of alcohol prevention programs for these parents, which could reduce the onset of children’s drinking.