Adolescence, defined as ages 10 and 24 years, is a period of development related with sexual discovery, exploration, and risk taking. Internetâ€™s appeal as a sex education resource has increased in this digital age. This study seeks to explore the internet as a source of sexuality education and its influence on sexual behaviours among adolescent students of the University of Lagos, Nigeria. The multistage sampling technique was used to recruit the participants for this study. A self-administered questionnaire was used to collect data from 399 students. The reliability of the questionnaire was tested using Chrobachâ€™s Alpha and the coefficient was 0.72 which showed that the instrument was reliable. Data were analyzed using descriptive statistic tools and the Spearman correlation (at p<0.05). Results showed that tendencies to use the internet as a source of sex education was more among the examined adolescents (75%) and 58% had regular access to the internet mostly on their cell phones. With an overall mean of 72%, the respondents had good knowledge of sexuality education. Also, with an overall mean of 81%, the considered factors (peer pressure, availability of information from parents and teachers, ease of internet access and satisfaction from online-sourced information on sex) played a major role in motivating adolescents to seek sex information through internet. Most of the respondents (57%) perceived that the internet influences adolescent sexual behaviour. The result of the interrelation between internet use, knowledge about sexuality education and sexual behaviour showed use of internet significantly influenced knowledge about sexuality and adolescentsâ€™ sexual behaviour. The study recommends more efforts to be made by educational institutions and health policy makers in addressing the peculiar present age needs of the adolescents in regards to sex education information delivery and the monitoring of proper use of the internet.