Background. Intimate partner violence (IPV) among adolescents is common worldwide, but our understanding of perpetration, gender differences and the role of social-ecological factors remains limited. Objectives. To explore the prevalence of physical and sexual IPV perpetration and victimisation by gender, and associated risk and protective factors. Methods. Young adolescents (N=2 839) from 41 randomly selected public high schools in the Western Cape region of South Africa (SA), participating in the PREPARE study, completed a self-administered questionnaire. Results. The participants’ mean age was 13.65 years (standard deviation 1.01), with 19.1% (541/2 839) reporting being victims/survivors of IPV and 13.0% (370/2 839) reporting perpetrating IPV. Girls were less likely to report being a victim/survivor of physical IPV (odds ratio (OR) 0.72; 95% confidence interval (CI) 0.57 - 0.92) and less likely to be a perpetrator of sexual IPV than boys (OR 0.33; 95% CI 0.21 - 0.52). Factors associated with perpetration of physical and sexual IPV were similar and included being a victim/survivor (physical IPV: OR 12.42; 95% CI 8.89 - 17.36, sexual IPV: OR 20.76; 95% CI 11.67 - 36.93), being older (physical IPV: OR 1.26; 95% CI 1.08 - 1.47, sexual IPV: OR 1.36; 95% CI 1.14 - 1.62), having lower scores on school connectedness (physical IPV: OR 0.59; 95% CI 0.46 - 0.75, sexual IPV: OR 0.56; 95% CI 0.42 - 0.76) and scoring lower on feelings of school safety (physical IPV: OR 0.66; 95% CI 0.57 - 0.77, sexual IPV: OR 0.50; 95% CI 0.40 - 0.62). Conclusions. Physical and sexual IPV was commonly reported among young adolescents in SA. Further qualitative exploration of the role of reciprocal violence by gender is needed, and the role of ‘school climate’-related factors should be taken into account when developing preventive interventions.