The present study explores the antecedents of first- and second-generation (1G and 2G) immigrant students' academic performance using PISA 2018 data. The study draws on an international sample of 11,582 students from 534 schools in 20 countries and focuses on PISA schools that catered to a mix of 1G and 2G students. The study explores the role that student attributes, student-perceived peer and parental support, school provisions, and school equity-oriented policies have on immigrant student academic achievement. The analysis involved specifying three separate stepwise multi-level regression models for mathematics, science, and reading achievement. Findings suggested that, at the within-school level, perceived parental support and teacher enthusiasm and the adaption of instruction were associated with improved academic performance, while student experience of bullying was associated with more substantive negative academic outcomes. At the between-school level, the opportunity to participate in creative extracurricular activities was associated with improved academic performance. In contrast, a higher proportion of 1G students and the overall perceived level of bullying of immigrant students were associated with substantively negative academic outcomes between schools. Tests of moderation effects suggested that parental emotional support appeared to be of particular relevance to 1G students' math and reading outcomes, while enhanced SES status appeared to be specifically relevant to improved science and reading outcomes for 1G students. Implications for policy and practice are discussed.