Mobile social media has become indispensable to university students' communication with various socio-demographic populations, exposing them to diverse social networks and augmenting their network heterogeneity. Although the psychological ramifications of network heterogeneity have been extensively examined, its correlated academic outcomes remain inconclusive. The current study formulated an integrated theoretical research model based on the stressor-stress-outcome framework to investigate the influence of factors associated with network heterogeneity (specifically, privacy invasion, social comparison, self-presentation, and excessive WeChat use) on social media exhaustion, psychological well-being, and academic well-being among university students. Furthermore, the research examined the mediating effect of social network exhaustion among network heterogeneity, psychological well-being, and academic well-being. A cross-sectional survey of 1128 WeChat users revealed that social comparison and excessive WeChat use had positive associations with social network exhaustion, while privacy invasion and self-presentation were negatively correlated with social network exhaustion. Additionally, social network exhaustion was negatively correlated with psychological well-being and academic well-being. Furthermore, social network exhaustion mediated the influences of network heterogeneity on psychological well-being and academic well-being. These obtained results could contribute to a more nuanced understanding of the underlying causes of social network exhaustion and the multifaceted effects of network heterogeneity. These insights may prove valuable for practitioners to enhance university students’ psychological states and academic performance in the contemporary mobile media-saturated environment.