Adolescents aged 10-24 years old are susceptible group to premarital sex, drugs abuse, and HIV/AIDS infection. Papua is the largest contributor to AIDS/HIV number in Indonesia. To overcome such problem, Rutgers WPF formed Dunia Remajaku Seru!(DAKU!), an intervention program towards adolescent reproductive health at senior high school level. This study aimed to determine psychosocial determinants of risky sexual behavior among senior high school students in Merauke District through cross-sectional approach. Samples were 1,364 second grade students that got DAKU!Program and matching process was conducted on schools that did not get DAKU!Program. Data analysis included univariate analysis, bivariate (chi square test) and multivariate (logistic regression test). Results showed that variables significantly related to adolescent risky sexual behavior were peer group with negative behavior, self-efficacy, parents'control, exposure to DAKU!Program and sex. Meanwhile, based on multivariate analysis, peer group with negative behavior (RP = 4.7 CI = 2.8 - 7.7) was the most dominant factor influencing risky sexual behavior.