There are limited studies on the prevalence and correlates of sexual risk behavior among adolescents in Pacific Island countries. In order to inform public sexual and reproductive health interventions, the aim of this study was to assess the prevalence and correlates of various sexual risk behaviors among in-school adolescents in 4 Pacific Island countries using data from the Global School-Based Health Survey. In a cross-sectional study, 6792 school-going adolescents (49.7% boys and 50.3% girls; 13-16 years old) from Fiji, Kiribati, Samoa, and Vanuatu were surveyed with a self-administered questionnaire. Overall, 18.9% of students reported to ever had sex (ranging from 12.9% in Vanuatu to 57.5% in Samoa), and of those sexually active, 38.0% had an early sexual debut (<14 years), 38.1% had 2 or more sexual partners during their lifetime, 39.5% had not used a condom at last sex, 50.9% had not used birth control at last sex, and 77.8% engaged in sexually risky behavior using a composite measure. Multivariate logistic regression found that male sex, older age, tobacco use, alcohol use, mental distress, having no close friends, and truancy were associated with several of 5 or all 5 sexual risk behaviors. Sexual and reproductive health promotion programs are indicated to address the high risk of sexually transmitted infection, HIV, and pregnancy in this adolescent population.