A considerable body of research has demonstrated the pivotal roles played in digital reading by self-regulated learning (SRL) and affective learning. Yet, whether teacher support facilitates SRL and affective learning has hitherto remained unclear. This cross-cultural study adopted multilevel latent profile analysis (LPA) to establish latent profiles of adolescents' SRL and positive affect, explored how such profiles were differentially correlated to digital-reading performance, and examined how perceived teacher support predicted profile memberships, at both student and school levels. Using data collected from 34,000 students nested in 1,100 schools from three Asian and three Western educational systems by the Programme for International Student Assessment 2018, single-level LPA revealed three or four student profiles, in associations with disparate digital reading. While self-regulatory strategies were decisive in profile assignment, emotions did not vary significantly across profiles or predict performance. The least self-regulated learners often fell into a vicious circle of poor emotional well-being and low performance, but highly selfregulated and capable digital readers did not necessarily report the most positive emotions. Multilevel LPA identified two or three school profiles based on relative frequency of student profiles, in relations to different school-mean digital reading. Students' perceived teacher support significantly predicted student-profile memberships; greater support increased likelihoods of being stronger self-regulated learners. But such support did not predict school-profile memberships. East-West cultural variations existed in all the influential patterns.