Abstract: This study determined the influence of socio-cultural and economic environment on adolescents’ sexual behavior. Knowledge, attitude and beliefs were used as mediating variables to environment factor and adolescents’ sexual behavior. The study used the descriptive-correlation research design. Two hundred ninety adolescents ages 11 -19 years old from two high schools and two universities from Region IV-A in the Philippines, chosen through simple random sampling were the respondents of the study. The results show that socio-cultural (school) environment, attitude and knowledge were significantly related to sexual behavior. Meanwhile, family and community socio-economic environments were negatively related to sexual behavior. Sexual behavior of adolescents differed when their age and gender were considered. Males who are in their late adolescence tend to engage more in risky sexual behaviors than those who were in their mid- adolescence and in their early adolescence. Attitude, age, gender and economic environment predict adolescent’s sexual behavior. Based on model generated socio-cultural environment, socio-economic environment had indirect effect to sexual behaviors of the adolescents. Knowledge fully mediates the relationship between socio-cultural (school) environment and sexual behavior. Beliefs and attitude were not found to be significant mediators.