Individual and family factors have been hypothesized to influence adolescent sexual behavior, but the extent to which this is true for adolescents in Jamaica as a whole and for those in rural areas in particular, has not been well studied. The objective of this study was to identify individual and family factors associated with initiation of sexual activity before the age of 16 among rural adolescents in Jamaica. We analyzed data for 469 sexually experienced adolescents attending public high schools in the rural parish of Hanover. Multivariate logistic regression was used to predict independent influences of these factors. The mean age at sexual debut was 11 years for boys and 15 years for girls. Early adolescent sexual activity was associated with liberal attitudes about negative sexual outcomes (OR = 1.96, 95%CI = 1.34-2.87) and first sexual partner not being a steady boyfriend or girlfriend (OR = 4.19, 95%CI = 1.62-10.84). Female gender (OR = 0.16, 95%CI = 0.07-0.36) and older age at time of survey were protective (OR = 0.40, 95%CI = 0.32-0.52). Girls who were early starters were more likely to have been initiated by partners who were not steady boyfriends. They also reported liberal attitude towards negative sexual outcomes. Boys were mainly influenced by liberal attitude towards negative sexual outcomes. Being older was protective for both genders. Considering the high rates of HIV and adolescent pregnancy in this population, reproductive health programs that attempt to delay age at first sex should begin early in primary school before adolescents become sexually active.