No studies have considered that parental mediation could be intrusive to adolescents' privacy and could lead to an increased risk of internet addiction. By integrating communication privacy management theory and parental monitoring research, this study examines the relationships among maternal mediation, adolescents' perceptions of privacy invasion, defensive responses to privacy invasion, and internet addiction. The participants were 678 13- to 16-year-old adolescents and their mothers who participated in the study for two consecutive years. Mothers reported their use of mediation strategies at Time 1; adolescents reported their perceptions of privacy invasion in terms of internet use and their defensive responses to privacy invasion at Time 2 and their internet addiction at Time 1 and Time 2. The results indicated that maternal restrictive mediation was associated with adolescents' perceptions of privacy invasion and that perceptions of privacy invasion were associated with defensive responses, which led to increased internet addiction. Adolescent females and males showed similar relationships. The findings emphasize the importance of parents' respect for adolescents' privacy boundaries and suggest that parents should adopt more communication-based mediation strategies to regulate adolescents' internet behaviors.