Background: Social media technology has provided platforms for enhanced human communication and expanded opportunities for self-expression. Despite the numerous gains, this social networking media, come with myriads of limitations; one being the tendency to be abused and/or misused, especially by young people or the young at heart. This study examined how social networking media influence the sexual behaviours of university undergraduates in Nigeria. Materials and Methods: The survey research method was adopted. A sample size of 396 students was determined using the Taro Yamane's formula. The study was anchored on the Technological Determinism theory. Data were collected through a structured questionnaire with a reliability coefficient of 0.99 through test-retest method. Data collected were analysed using descriptive statistics with the aid of SPSS v25 software. Results: Findings showed, amongst others that, undergraduates in Nigerian universities are largely exposed to a substantial amount of sexual contents on various social media networks; and that this exposure negatively influences their psychology towards sex as manifested in the area of dating before marriage as a result of indulgence in interactive and romantic sites. Conclusion and Recommendations: The study recommends the introduction of social media education in higher institutions to help enlighten students on the responsible use of these technologies to minimize the inherent weaknesses and maximize the intrinsic values of utilising these media platforms.