Internet use has become an integral part of youth’s everyday life. While the Internet brings convenience for information access, communication, and entertainment (e.g., Thorsteinsson & Davey, 2014; Wallace, 2014), when the mechanism of Internet use becomes maladaptive, a phenomenon called problematic Internet use (PIU) arises. PIU among youth has been defined as excessive or maladaptive use of online activities, which interferes with youth’s development, academic performance, and social life in negative ways (Beard & Wolf, 2001; Ceyhan, 2008; Ioannidis et al., 2019). Across the world, China was the first country that recognized PIU as an official mental health concern, given the significantly high and increasing trend of PIU prevalence rates among Chinese youth (Jiang & Leung, 2011). Previous research has well-documented the detrimental outcomes of PIU among Chinese adolescents. However, there has been a lack of investigation on the etiology of PIU from a social and cognitive perspective. In Study 1, structural equation modeling (SEM) was used to empirically identify how PIU differed between students’ sex, family income level, and left-behind status as well as to examine the relations between SEL competencies and PIU. Results yielded that male students endorsed higher levels of PIU and time management on the Internet than female students, whereas no differences were observed across family income levels and left-behind status. In addition, students with higher levels of SEL competency and all five core domains of SEL competencies (i.e., responsible decision-making, social awareness, self-management, self-awareness, and social relationship) reported less frequent PIU, illustrating the preventative roles of SEL competencies on PIU. Based upon Study 1, Study 2 considered social factors additional to the cognitive factors when studying the etiology of PIU. Similar to Study 1, SEM was used to examine the associations between traditional bullying and cyberbullying victimization and PIU, and the moderating effects of SEL competency and five core SEL domains on the associations between traditional bullying and cyberbullying victimization and PIU. Upon controlling for students’ demographic variables, the study found that students who experienced more frequent traditional bullying and cyberbullying victimization reported a higher level of PIU. SEL competency, social-awareness, relationship skills, and self-awareness exacerbated the positive relationships between traditional bullying victimization and PIU. Taken together, the findings from both studies supported the preventive roles of SEL competencies and detrimental roles of bullying victimization on PIU and revealed the promoting effects of both overall and domain-specific social-emotional attributes in PIU development when youth faced bullying, which intended to inform and facilitate the preventative and interventive efforts on Chinese adolescents’ bullying victimization and PIU.