Comprehensive Sexuality Education is a sex education instruction method based on a curriculum that aims to give students the holistic knowledge, attitudes, skills, and values to make healthy and informed choices in their sexual lives. This study aims to evaluate the Effectiveness of Comprehensive Sex Education Training Program on Knowledge, Attitude and Belief Regarding Safe Sexual Health Practices Among Higher Secondary Students in The Selected Schools of Vadodara. A pre-experimental (one group pre-test and post-test), evaluative research approach was used to achieve the objectives of the study on 202 students of class eleventh using a purposive sampling method. Results regarding knowledge showed that mean post-test knowledge score was 24.1 (3.11) higher than mean pre-test knowledge score 14.80 (2.87) with mean difference of 9.38 and obtained (t value=33.66, df=201, p=0.001) was found statistically highly significant at p<0.05 level. While assessing attitude in post-test 183(90.6%) had favourable attitude and 19(9.4%) had unfavourable attitude and same while checking belief in post-test 168(83.2%) had rational belief and 34(16.8%) had irrational belief regarding safe sexual health practices of higher secondary students Correlation was used for identifying that there is no relationship between knowledge, attitude and belief with socio demographic variable towards regarding safe sexual health practices of higher secondary students .