This study aimed to investigate gender differences in reasoning influencing the postponing of sexual debut among university youth in Lebanon. Findings aimed to develop understandings that might help inform future research on, and programme implementation of, young people's reproductive and sexual health. A cross-sectional survey of sexuality and sexual practices, attitudes and perceptions was conducted among private university students in Lebanon using a secure online method. Of 1838 participating students, 48.7% indicated they had never engaged in oral, anal or vaginal sex (i.e., penetrative sexual activity) during their lifetime (n = 895). Common socio-cultural concerns regarding sexual initiation included: gaining a bad reputation (47%), social rejection (58%), religion (70%) and parental disapproval (61%). Women were four times more concerned than men regarding loss of reputation and self-respect, six times more so regarding parental disapproval and three times more likely to be concerned with societal disapproval. Intrapersonal concerns included fear of contradicting one's own beliefs (67%), feeling guilty afterwards (62%) and losing self-respect (55%). Women were four times more likely to feel loss of self-respect and six times more likely to think sex was disgusting. Underlying reasons for postponing sexual intercourse are linked to adopted fears and social pressures that are internalised, and reinforce existing gender inequalities and reaffirm discriminatory gender norms.