Guided by Self-Determination Theory and Social Cognitive Theory, this study aimed to investigate the risk effect of dissatisfaction in psychological need on Internet gaming disorder (IGD), as well as the potential mediating effects of a generic sense of purpose in life and maladaptive gaming-specific outcome expectancy beliefs. With a cross-sectional design, 525 Chinese university students (M_age = 20.18 years, SD_age = 1.62; 53.7% male) voluntarily completed an anonymous paper-and-pencil questionnaire regarding their Internet gaming. Our findings showed that, as hypothesized, students’ dissatisfaction in need for relatedness correlated negatively with purpose in life and IGD tendency, and positively with negative outcome expectancies of reducing gaming. IGD tendency also correlated negatively with purpose in life and positively with negative outcome expectancies. Moreover, results of a path analysis with bootstrapping showed support for a partial mediating effect of negative outcome expectancies of cutting back gaming on the relationship between relatedness need dissatisfaction and IGD tendency. The study will provide practical insight into the design of cost-effective school-based IGD-prevention/intervention programs.