Between the years of 2003–2015, the Programme for International Student Assessment (PISA) has identified a global trend signalling a decline in a sense of school belonging for secondary school students. Research has identified several factors that are positively related to school belonging, such as teacher support and academic motivation. However, little empirical research has been conducted to evaluate the relevant school belonging variables holistically and to assess their socio-ecological levels (e.g., student, microsystem, mesosystem) relative to the student. The purpose of this study is to assess the significant predictive variables within each socio-ecological level regarding school belonging. For this purpose, this study used data collected by PISA in 2015, focusing on data from 309,785 15-year-old students attending 12,668 schools in 52 countries around the world. Hierarchical multiple regression analysis was conducted to a) examine the empirical support for a layered structure of sense of school belonging, b) explore the contributions of variables in each layer of the socio-ecosystem to explain the variability in sense of school belonging and c) examine potential variations in this ability across schools and countries. The models provided support for the existence of such layers but also for some underlying relationships across the variables in the layers of the socio-ecosystem. The study then concludes with a discussion of the implications of the findings for school leaders, teachers and parents with respect to how school belonging approaches and strategies can be absorbed into existing practices and operations at school. Highlights: Student, or individual intrapersonal factors, can have significant impact on a student's perception of belonging. The strongest individual factors were collaboration dispositions (i.e., enjoying and valuing cooperation with others). Findings suggest a significant negative relationship between school belonging and test anxiety. It can be concluded that there are various systemic influences of school belonging.