The study examined gender and age differences in the relationship between sensation seeking and sexual risk behaviors among secondary school students in Kenya. The study was conducted in Kisumu Municipality. Kisumu was chosen as it is one of the leading regions in HIV prevalence, estimated at 15%. The HIV prevalence was assumed to indicate a positive relationship between sensation seeking and high sexual risk-taking behavior. A sample size of 357 adolescents (44% males and 56% females) was drawn using a stratified sampling method from a population of 10,278 secondary school students. Descriptive statistics were used to analyze quantitative data, while the qualitative data was summarized thematically. The study's findings indicated that about half the adolescents were highly sensational seekers predisposing them to take risks. There also existed significant gender differences in the prevalence of sensation-seeking and sexual risk-taking behavior, with the male adolescents being higher risk-takers than their female counterparts. Similarities in the prevalence of sensation-seeking were also reported. However, this varied across ages and different gender. Female adolescents' sensation-seeking increased earlier in life than their male counterparts. Further, the study indicated gender differences in the adolescents' tendency to indulge in sexually risky behaviors due to their sensation-seeking. This behavior tendency was higher for males than for female adolescents. Additionally, the results indicated significant age differences, with the susceptibility to indulge in such risky behaviors increasing with advancement in age.