PURPOSE: The purpose of this study was to evaluate the impact of a rights-based sexuality education curriculum on adolescents' sexual health behaviors and psychosocial outcomes 1 year after participation. METHODS: Within 10 urban high schools, ninth-grade classrooms were randomized to receive a rights-based curriculum or a basic sex education (control) curriculum. The intervention was delivered across two school years (2011-2012, 2012-2013). Surveys were completed by 1,447 students at pretest and 1-year follow-up. Multilevel analyses examined curriculum effects on behavioral and psychosocial outcomes, including four primary outcomes: pregnancy risk, sexually transmitted infection risk, multiple sexual partners, and use of sexual health services. RESULTS: Students receiving the rights-based curriculum had higher scores than control curriculum students on six of nine psychosocial outcomes, including sexual health knowledge, attitudes about relationship rights, partner communication, protection self-efficacy, access to health information, and awareness of sexual health services. These students also were more likely to report use of sexual health services (odds ratio, 1.37; 95% confidence interval, 1.05-1.78) and more likely to be carrying a condom (odds ratio, 1.97; 95% confidence interval, 1.39-2.80) relative to those receiving the control curriculum. No effects were found for other sexual health behaviors, possibly because of low prevalence of sexual activity in the sample. CONCLUSIONS: The curriculum had significant, positive effects on psychosocial and some behavioral outcomes 1 year later, but it might not be sufficient to change future sexual behaviors among younger adolescents, most of whom are not yet sexually active. Booster education sessions might be required throughout adolescence as youth initiate sexual relationships.