BackgroundParent–child relationships, the rearing attitudes of parents toward their children as well as the interactive relationships, such as play and cultural activities that parents and children enjoy together, serve as important factors in predicting a child’s growth and development. These experiences of annual events celebrated with the family may be related to the school-age child’s development. However, this relationship has not been investigated sufficiently. Therefore, this study aimed to identify the relationship between the experience of annual events observed in the family and a child’s social adjustment.MethodsIn 2019, a self-administered questionnaire survey targeting fifth graders (ages 10–11) in Japan was conducted with children’s parents. Major survey items included participants’ characteristics (child’s sex, family composition, siblings, household income, and parents’ educational backgrounds), annual events observed in the family (Setsubun or the day before the start of spring, Mother’s Day, Father’s Day, the Tanabata or Weaver Festival, Respect for the Aged Day, Winter solstice, etc.), and the child’s social adjustment (Strengths and Difficulties Questionnaire). A total of 653 children who met the criteria of not having any developmental disorders were included as participants for the analysis.ResultsThe participants had celebrated an average of 15.47 (± 5.52) annual events with their families that year. The number of annual events celebrated was significantly related to family composition and the parents’ educational backgrounds. We found that children who came from families with numerous experiences of annual events were more likely to have higher prosocial behavior and were less likely to have externalizing or internalizing problems. The same pattern was found even after adjusting for the family’s socioeconomic background and other factors; that is, children who came from families having diverse experiences of annual events were more likely to show prosocial tendencies.ConclusionsOur findings suggest that the experience of annual events observed with family potentially enhances a child’s prosocial behavior. Thus, celebrating and preserving cultural and personal events in the amily context may be an important developmental experience in terms of children’s social adjustment.