Background: Social networking has become integral to the intellectual, emotional and social lives of the young. The often-unrestricted access to sexually explicit content on the social media and associated adverse sexual health among this group, constitute key outcomes in public health research. Aim: To determine social media use and the effect on sexual practices among undergraduate students in a private university in Southern Nigeria. Methodology: This descriptive cross-sectional survey among 300 undergraduate students of Madonna University Nigeria, Elele campus, was conducted between June and November, 2019. Respondents were selected using multistage sampling technique. Data were obtained using self-administered semi-structured questionnaires. Data analysis employed statistical package for social sciences version 22.0. Chi-square test was used to determine statistically significant associations between variables at p values < 0.05. Results:  Out of a sample size of 300, all were returned and analysed, giving a response rate of 100%, and a mean age of 21.85+ 2.63years. The awareness of social media was 97.9%, with commonest 237 (79%) from friends/peers. The reasons cited for its use include: 208 (72.7%) access to news, 182(63.6%) academics, while 173 (60.5%) accessed social media for sexually explicit content. The mean age at sexual debut was 17.44 + 2.63 years. There were associations between use of social media for sexually explicit content and [the sexually active (p=0.000); type of sexual acts practised (p=0.003) and number of sexual partnerships (p=0.000)] respectively. Conclusion: This study found an association between use of social media for sexually explicit content and risky sexual practices. No association was found between ever had sexual act and gender. We recommend behaviour-change interventions that control social media use for sexually explicit content and not compromise access to sexual health education among them.