Young people worldwide are now at increased risk of unsafe sexual behavior; it is thus imperative to understand the determinants of such practices among them. To assess factors associated with Risky Sexual Behavior (RSB) among secondary school students in Nigeria. This cross-sectional study was conducted using multistage sampling technique among 375 secondary school students in Ogbomoso, Nigeria. A pretested questionnaire was used for data collection; chi-square test and binary logistic regression analysis were done. Overall, 23.0% of the respondents had at least one RSB; students not in steady relationships were 5 times more likely to have RSB ( OR = 4.50, 95% CI [2.66, 7.71]). Also, respondents who had positive attitude toward RSB had 24% increased odds of RSB practice compared with those with negative attitude ( OR = 23.75, 95%CI [2.48, 22.78]). The burden of RSB is high among secondary school students in South West Nigeria. There is urgent need for reprogramming of sex education for the Nigerian secondary school students.