There is limited prospective research on the relation between school connectedness (i.e., the extent to which students feel accepted, valued, respected, and included in the school) and mental health symptoms in adolescents. A sample of 2,022 students (999 boys and 1,023 girls) ages 12 to 14 years were measured at 2 time points (12 months apart) on school connectedness and mental health symptoms (general functioning, depression, and anxiety symptoms). School connectedness correlated extensively with concurrent mental health symptoms at both time points (between 38% and 55% covariation with depression, 26% to 46% with general functioning, and 9% and 16% for anxiety symptoms). Using hierarchical linear modeling, school connectedness also predicted depressive symptoms 1 year later for both boys and girls, anxiety symptoms for girls, and general functioning for boys, even after controlling for prior symptoms. The reverse, however, was not true: Prior mental health symptoms did not predict school connectedness 1 year later when controlling for prior school connectedness. Results suggest a stronger than previously reported association with school connectedness and adolescent depressive symptoms in particular and a predictive link from school connectedness to future mental health problems.