Aim: This study aims to determine the effect of comprehensive sexual education on improving knowledge, attitudes, and skills in preventing premarital sexual behavior. Design: Quasi-experimental pre-post-test design with a control group. Methods: The participants in this study were SMKN 1 Cibadak students. 60 respondents were divided into two groups (intervention group = 30 and control group = 30). The purposive sampling technique selected participants with the following inclusion criteria: grade 9 students who are already dating. In the intervention group, comprehensive sexual education was conducted for six sessions, consisting of six main topics. The research instrument was a knowledge, attitudes, and skills questionnaire which had previously been tested for validity and reliability using the Shapiro-Wilk and Levene test. The collected data were processed using SPSS version 25.0 and analyzed by univariate (frequency and percentage), bivariate (paired t-test and independent t-test), and multivariate (linear regression test). Results: Comprehensive sexual education significantly improved knowledge, attitudes, and skills in preventing premarital sexual behavior with a p-value = 0.000. The difference in each variable's mean and standard deviation significantly occurred between the intervention and control group with the results of knowledge ( 17