This study was conducted to examine the characteristics and use of dietary supplements by preschool children in Japan. A survey was conducted among 2,125 parents of preschool children to discover the status of dietary supplement use and their attitudes towards supplement use by their children. Logistic regression models were used to determine which characteristics predict supplement use in this population. For detailed characterization, child supplement users were also categorized as either the users of vitamins and minerals only or the users of other supplement components. For parents of non-user children, the parent's knowledge and attitudes toward supplements for children were investigated. Fifteen percent of children had used dietary supplements. Two parent-related factors were especially important, the frequency with which they referred to nutritional labels and their own supplement use, which had a significant encouraging effect on their children's supplement use. The parents of child supplement users showed limited awareness of the government system concerning diet and food, placed safety over efficacy, selected products with natural ingredients, and did not seek consultations with professionals. These parents, especially those who were aware of the specially designed supplements for children, exhibited positive responses to supplement use by their children. It is likely that parents' knowledge and attitudes toward dietary supplements and nutrition have a striking effect on their children's use of supplements. Unfortunately, their knowledge at present was less than satisfactory. More accurate information on nutrition, dietary intake and dietary supplements must be disseminated.