This study investigates youths’ perceptions of privacy, privacy concerns, and privacy behaviour among active Facebook and Instagram users in Nigeria. It also examines the association between privacy concerns and self-disclosure, the influence of gender on self-disclosure, and the manifestation of the privacy paradox on social media. Drawing on Altman and Taylor’s Social Penetration Theory, the study adopted a survey research design and surveyed 389 undergraduates systematically selected from two government-owned institutions in Kwara State using a multistage stratified sampling technique. The findings reveal the manifestation of the privacy paradox among Nigerian youths, as respondents reported disclosing in-depth personal information online despite expressing concerns about their privacy. The study also found that youths had moderate privacy concerns and perceived social media as an open and potentially dangerous environment for privacy. A significant positive and moderate association was found between privacy concerns and self-disclosure (r = 0.436, p < .001), indicating that greater privacy concerns were associated with higher levels of self-disclosure. Gender also significantly influenced self-disclosure, with male respondents reporting higher levels of self-disclosure than female respondents (t(387) = 8.73, p < .001). The researchers recommend that social media platforms intensify user education on privacy policies and provide timely awareness of the potential consequences of disclosing sensitive personal information online.