BACKGROUND: Studies of the impact of mental disorders on educational attainment are rare in both high-income and low- and middle-income (LAMI) countries. AIMS: To examine the association between early-onset mental disorder and subsequent termination of education. METHOD: Sixteen countries taking part in the World Health Organization World Mental Health Survey Initiative were surveyed with the Composite International Diagnostic Interview (n=41 688). Survival models were used to estimate associations between DSM-IV mental disorders and subsequent non-attainment of educational milestones. RESULTS: In high-income countries, prior substance use disorders were associated with non-completion at all stages of education (OR 1.4-15.2). Anxiety disorders (OR=1.3), mood disorders (OR=1.4) and impulse control disorders (OR=2.2) were associated with early termination of secondary education. In LAMI countries, impulse control disorders (OR=1.3) and substance use disorders (OR=1.5) were associated with early termination of secondary education. CONCLUSIONS: Onset of mental disorder and subsequent non-completion of education are consistently associated in both high-income and LAMI countries.