The purpose of this study is to verify the moderation of child developmental stage and gender in the effects of parental internet-use controlling parenting behaviors (internet control behavior) and warm/rational parenting style (warm/rational parenting) on child internet addiction. Two-hundred-thirty 3rd graders (105 male children and 125 female children) and 216 8th graders (126 male adolescents and 90 female adolescents) residing in Seoul participated in the study by filling out the self-report internet addiction scale, parental internet-use controlling behaviors scale, and parental warm/rational parenting style scale. The correlation analyses and hierarchical regression analyses including an interaction term (either warm/rational parenting×gender or internet control behavior×gender) were conducted to address the research questions. The study found a significant moderation of child developmental stage and of child gender only in the relationship between internet control behavior and child internet addiction, not in the relationship between warm/rational parenting and child internet addiction. Specifically, this study found a negative effect of parental internet control behavior on child internet addiction only in the male adolescent group. For the rest of the groups (male and female child groups and female adolescent group), high levels of parental internet control behavior were related to low levels of child internet addiction, revealing beneficial effects of parental internet control behavior on child internet addiction. On the other hand, no significant moderation of the child developmental stage and gender was found between parental warm/rational parenting and child internet addiction, revealing that parental warm/rational parenting decreased levels of child internet addiction in all four groups (male child, female child, male adolescent, and female adolescent groups). The study suggests that parents need to understand their children’s developmental characteristics and gender when restricting their children’s internet use to yield better results on child problematic use of the Internet.