This study’s aim was to establish the relationship between peer pressure and high-risk sexual behavior among high school students in Kenya. Twenty-eight students were sampled per school from form 1 to 4, which summed to 138 students in Nakuru East Sub County. Primary data was gathered from the 138 students through a structured questionnaire. Interviews were conducted to the school head teacher. Only 120 respondents were able to fill in the questionnaires.This meant that the response rate was 87.6%. The focus group discussions were done successfully as well as the interviews scheduled with the head teachers. Quantitative data was analyzed through statistical package for social sciences (SPSS) using cross tabulation and chi-square to determine response frequency and percentage. Cross tabulation was used to analyze the variables using tables and was supported by qualitative data. The Pearson Chi Square was 0.00 indicating that peer pressure influenced high-risk sexual behavior among high school students in Nakuru East Sub County, Kenya. The study found that peer pressure influenced the students’ decisions on sex and relationships. The study concluded that peer pressure was an influence to high-risk sexual behaviour among high school students and the youth in general. It influenced the decisions they made on dating, sexual relationships, and sex. The study recommended that sex education should be included in the curriculum in order to help the students on gaining knowledge on life skills.