Approximately one-third of the world's population is between 10-24 years of age and twenty percent of Nigerians are adolescents. This study’s aim was to assess the impact of sex education intervention on knowledge attitude and practice of sexuality, among female adolescents in a female senior secondary school in Kaduna. The study was a quasi experimental study and the study population comprised senior female secondary school students. A multistage sampling method was used to select a sample size of 295 for the study and 283 for the control groups respectively. The study led to increased knowledge of adolescents sexuality after an intervention programme of family life education was taught. Students in the study group with positive sexual attitude also improved. Sexuality education has been shown in this study to improve the knowledge and attitude of students in the intervention group.