This study invokes the ecological approach to social support by examining how school social support relates to moderate or severe adolescent depression. School is seen as not only a place for supportive individual-level relationships, but also as a source of community support created by teachers and other students. The main purpose of the study is to examine whether school-level social support is related to adolescent depression and, if so, how much of the school-level differences in moderate or severe adolescent depression can be explained by school social support? The study is based on data included in the Finnish School Health Promotion Survey, which covers about 70% of Finnish 14- to 16-year-old adolescents. The data were collected in 2002–2003 and the analysis was conducted by employing multilevel logistic regression analysis. © 2008 Wiley Periodicals, Inc.