The thrust of this paper was to elicit socio-cultural predictors of risky sexual behavior among adolescents and young adults in Nigeria .Socio-cultural parameters were seen to be those factors in the social environment that influences behaviour. The socio-cultural theory believes that people learn through interactions within the socio-cultural environment and such interaction includes; home (parental influence, social economical status of family), peers and culture (religious practices, age norms, and gender issues). This paper further examines these factors and how they predict risky sexual behaviour such as early marriage ,non utilization of contraception, early sex initiation, induced abortions, having multiple sex partners, sex under the influence of alcohol, and indulging in sex for financial and material gains, among adolescents and young adults in Nigeria. It was therefore concluded that socio-cultural environment is a strong predictor of adolescent and young adult sexual risk behavior in Nigeria. Thus it was recommended that social cultural environment should be shaped for optimum reproductive health behaviour among adolescents and young adults in Nigeria.