This study analyses the role of social support in Internet use, focusing on when it leads to problematic or functional use in male and female adolescents. Three research hypotheses state: (1) when offline social support is low, online social support leads to a problematic Internet use; (2) when offline social support is high, online social support leads to a functional Internet use; (3) significant differences between male and female adolescents in both the online and offline dimensions considered. Results showed that the positive social interaction factor of online social support positively predicts problematic Internet use and that the latter is negatively affected by offline social support (affectionate dimension). Furthermore, online social support predicts functional Internet use (positive social interaction factor), while offline social support has no such effect. Finally, gender differences occur: males show higher problematic Internet use, and a higher number of friends and acquaintances than females, while females show higher online and offline social support than males. Implications of this research are particularly relevant for schools (e.g., teachers), families (parents, caregivers, etc.), and policy maker, so that they can support adolescents in the construction and development of offline friendly relationships and promote a functional use of the Internet for preventing its negative effects with active educational policies.