The study examined the relationship between teacher support and reading performance via the multiple mediation effects of reading engagement (emotional engagement and cognitive engagement). Data were extracted from Programme for International Students Assessment (PISA) 2018, with a sample of 171,429 adolescents from 5,692 schools across 22 countries/regions. Using multilevel serial mediation analysis, the results confirmed that teacher support enhanced adolescents' reading performance by fostering reading engagement. Emotional engagement and cognitive engagement worked in tandem and sequentially as serial mediators. Explicitly, the positive impact of teacher support on reading performance was positively mediated through emotional engagement solely, and serially mediated through emotional engagement and then cognitive engagement. Cognitive engagement also exerted significant mediating effects in most territories. The current study provides new findings in depicting the sole and simultaneous functions of emotional and cognitive engagement in relations with teacher support and reading performance with cross-national evidence. It also suggests the practical implications for instructors to apply various pedagogical interventions to support adolescents' reading performance growth.