Abstract The objective was assess the influence of untreated caries and socioeconomic status (SES) on school dropout among adolescents. A six-year cohort study was conducted with random sample of adolescents (12 years-old) who had been evaluated initially in 2012 from Santa Maria, Brazil. Sex, socioeconomic status (mother’s education and household income), and untreated caries were collected at the baseline. The outcome variable was collected at the follow-up through self-report and was divided into three categories: adolescents who only studied, who studied and employed, and who school dropouts. A multinomial regression model was performed to assess the influence of oral disease and SES on school leaving, through relative risk ratio (RRR) and 95% confidence interval (95% CI). From of 1,134 adolescents evaluated at the baseline, 768 participants with a mean age of 17.5 years were re-evaluated at follow-up (67.8% response rate). Male (RRR: 2.31; 95%CI: 1.19-4.48) and adolescents with untreated caries at the baseline had an increment in school-leaving (RRR: 2.26; 95%CI: 1.12-4.56). Mothers with low education (RRR: 2.24; 95%CI: 1.09-4.61) had a higher probability of having children who leave school. Untreated caries and low SES in early adolescence can influence the tendency to school dropouts.