OBJECTIVES: We investigated whether perceived social support among adolescent students moderated the association between violence exposure and internalising symptoms in São Paulo city, Brazil. METHODS: We tested the stress-buffering model using data from the cross-sectional school-based, survey São Paulo Project on the Social Development of Children and Adolescents. Internalising symptoms were measured using an adapted version of the Social Behaviour Questionnaire; serious victimisation, being bullied once/week, school violence and community violence, friend and teacher support were scales adapted by the research team; the Alabama Parenting Questionnaire measured parenting style. Linear mixed-effects models were used to quantify moderation effects of (i) social support between violence exposure and internalising symptoms and (ii) gender between violence exposure and internalising symptoms across schools. RESULTS: Across schools, being bullied once/week, school violence, and community violence were associated with a significant (p<0.001) increase in internalising symptoms (e.g., bullied b = 5.76, 95% CI 2.26, 9.26; school violence b = 0.48, 95% CI 0.30, 0.67; community violence b = 0.36; 95% CI 0.22, 0.50). Males exposed to all types of violence had significantly lower (p<0.01) internalising symptoms compared to females (e.g., serious victimisation: b = -1.45; 95% CI -2.60, -0.29; school violence b = -0.27; 95% CI -0.30, -0.24; community violence b = -0.23; 95% CI -0.25, -0.20). As a main effect, social support was associated with a significant (p<0.01) decrease in internalising symptoms across schools (e.g., positive parenting b = -2.42; 95% CI -3.12, -1.72; parent involvement b = -2.75; 95% CI -3.32, -2.17; friend support b = -1.05; 95% CI -1.74, -0.34; teacher support b = -0.90; 95% CI -1.58, -0.22). Social support did not moderate the association between violence exposure and internalising symptoms. CONCLUSIONS: Adolescent students in São Paulo exposed to violence have a higher likelihood of internalising symptoms, compared to those who are not. Support from parents, friends, and teachers, independent of violence, appear to be protective against internalising symptoms, pointing to potential programmes that could improve adolescent mental health.