Problematic Internet Use (PIU), with its adverse health outcomes, is a clinically established phenomenon that is not formally diagnosable yet. The latest PIU research reveals differential psychological mechanisms underlying two types of Internet usage: social use (like using social media, chatrooms, and others) and non-social use (like live streaming, short-form video viewing, and others). Social forms of PIU often signal underlying interpersonal issues, including loneliness, attachment problems, and social skill deficits. In comparison, non-social usage might indicate emotion regulation problems, including emotion recognition deficits, poor cognitive empathy, and emotion suppression. A common developmental concomitant of these functions is the ability to mentalize, operationalized as Reflective Functioning (RF). While studies supporting the role of impaired RF in problematic social uses of the Internet abound, only a few studies relating RF deficits to non-social PIU are identifiable. Also, mentalizing is multidimensional, with cognitive and affective poles influencing emotion regulation and interpersonal functioning. Deficits in both poles of mentalizing have been differentially implicated in non-social and social PIU. Based on the latest empirical evidence in Internet-use problems, the multifaceted role of mentalizing could be meaningfully assimilated into a novel social-cognitive model of PIU. To that end, the current paper attempts to theoretically integrate affective and cognitive mentalizing, with its roles in emotion regulation and interpersonal functioning, into Bandura’s Social-Cognitive Theory of PIU. The theoretical model might have implications in developing a mentalization-based treatment modality for PIU that could train individuals in efficiently regulating emotions and navigating real-life social situations without resorting to an over-involvement with the virtual world.