<p>This study examined whether mentalizing impairment and anxiety sequentially mediate the association between Internet addiction and academic engagement. Data were collected from 1,254 Chinese high school students by questionnaires. The results showed that Internet addiction significantly positively correlated with mentalizing impairment and anxiety, negatively with academic engagement. Academic engagement was affected by Internet addiction through three distinct pathways: the mediating effect of mentalizing impairment, the mediating role of anxiety, and the serial mediating effect of both mentalizing impairment and anxiety. The findings identify mentalizing impairment may be a direct cognitive consequence of Internet addiction, with anxiety serving as an emotional exacerbator that collectively diminishes students’ academic engagement. This study advances understanding of adolescents’ academic engagement by proposing and empirically supporting a cognitive–affective pathway in which Internet addiction is associated with lower academic engagement through mentalizing difficulties and anxiety, providing theoretical guidance for guiding the academic development of adolescents.</p>