Objective: To identify familial characteristics that may have influenced the effectiveness of a parent-based intervention to reduce unsafe sun practices in children aged 9 to 12 years (fourth through sixth grades). Design: Randomized control design with a 30-day follow-up. Setting: Participants were recruited from 2 distinct regions in the United States: southern Idaho and eastern Tennessee. Participants: Three hundred forty children were assigned to the experimental group in which the parents received the intervention materials. One hundred twenty-nine respondents were assigned to the control group. Intervention: The intervention provided materials that encouraged parents to communicate skin cancer risks, promote sun-safe behaviors, and discourage high-risk sun-related behaviors. Main Outcome Measures: Outcome measures included sunburn frequencies, sunburn severity, and sunbathing tendencies. The moderator variables were positive characteristics of the parent-child relationship, levels of negative communication, parental monitoring, and child compliance. Results: Sunburn frequency, sunburn severity, and sunbathing tendencies were most effectively reduced when the quality of the parent-child relationship was high, the child exhibited high levels of compliance, and there were low levels of negative communication. Conclusion: The findings of this study provide evidence that parents can be viable change agents for child behaviors and that the quality of the family relationship is critical to the success of such interventions.