The study aimed to assess the prevalence and correlates of sexual risk behaviours among adolescents in Mozambique. In the cross-sectional 'Global School-Based Health Survey (GSHS)', 1918 students aged 11-18 years from Mozambique responded to a questionnaire in 2015. More than half (57.4%) of the students ever had sex, 68.4% among boys and 45.8% among girls. Among students who ever had sex, 41.5% had early sexual debut (<14 years), 57.9% had multiple sexual partners, 25.0% had not used a condom and 42.0% had not used birth control at last sex, and 59.4% engaged in multiple sexual risk behaviour. In adjusted logistic regression analysis, alcohol use, school truancy, older age and male sex were associated with multiple sexual risk behaviours. A large number of adolescents in Mozambique reported sexual risk behaviours, emphasising the need for interventions.