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Smartphones have become an integral part of our lives, significantly affecting adolescents’ media consumption behaviors, and social issues such as smartphone addiction or problematic usage have been raised. Concerned parents have applied various mediation strategies; however, most were ineffective and created further conflicts between parents and adolescents. Contrary to the perceived seriousness of smartphone addiction, less than 10% of the users are actually diagnosed as in high-risk groups. Rather than treating those identified as addicts, preventive intervention strategies should be made available to broader populations to reduce overall problematic uses. This paper suggests a framework of preventive intervention programs to promote adolescents’ healthy smartphone use through a series of case studies. In the first study, three smartphone user groups with different usage motivations and behavior patterns were identified. In the second study, the difficulties in smartphone mediation process were compared from perspectives of both parents and children. The results indicated that each household with diverse family cultures need customized intervention programs. In the third study, parent–child dyads participated in mutual rule-shaping workshops to support adolescents’ healthy smartphone use and reduce conflicts. As a result, they were able to reflect their daily smartphone usage patterns and realized the necessity of a continuous negotiation process for rule-shaping according to usage contexts. Based on implications from these studies, we suggest activity design of online and offline integrated services system to facilitate adolescents’ healthy smartphone usage habits.