Objectives: This study examined the effects of maternal mediation and mother-child communication on children’s smartphone overdependence. It also explored the moderated moderation effect of mother-child communication and children’s gender on the relationship between maternal mediation and children’s smartphone overdependence.Methods: A total of 411 first to third grade elementary school students and their mothers participated in this study. Mothers responded to questionnaires. Data were analyzed using multiple regression analysis with SPSS 21.0 and using model 3 in PROCESS macro version 3.4.Results: First, maternal active mediation only affected girls’ smartphone overdependence, while maternal restrictive mediation affected both boys’ and girls’ smartphone overdependence. That is, the more active mediation mothers showed, the less dependent girls were on smartphones. Moreover, the more restrictive mediation mothers showed, the less dependent both boys and girls were on smartphones. Second, problematic communication influenced both boys’ and girls’ smartphone overdependence; that is, the more problematic communication they had with their mothers, the more they depended on smartphones. Lastly, the effect of maternal active mediation on children’s smartphone overdependence was different depending on open communication and children’s gender. Specifically, its effect on children’s smartphone overdependence was greater when they communicated more openly with their mothers, and this effect was only found in the case of girls.Conclusion: This study confirmed that maternal mediation and mother-child communication are important to effectively prevent or intervene in children’s smartphone overdependence. It also suggests that prevention or intervention should be approached differently depending on children’s gender.