Background: Family planning is the practice of controlling the number of children one has, preventing pregnancy and child spacing, particularly using contraception. It has allowed man to control family size, and prevent pregnancy at times not intended. The general name for techniques for preventing pregnancy in the initial days following sexual activity is emergency contraception (EC). These methods are intended to be used in the event of unplanned, unprotected or insufficiently protected sex; forced sexual contact; sexual assault; and contraceptive failures. Aim: To assess the factors influencing knowledge of family planning and the socio-demographic characteristics associated with knowledge of family planning among undergraduates in private and public universities in Osun State. Methodology: This study was a descriptive cross-sectional study design. The survey was carried out among 400 students in a public and a private school in Osun State. Data collection was done using a weekly structured self-administered questionnaire. The data collected was entered and analyzed using IBM SPSS version 25.0; P value was set at (P<0.05). Results: The significant socio-demographic determinants of knowledge were age in the private university, marital status in public university, tribe, and religion in both universities, father's highest level of education in both universities, mother's highest level of education in a private university, father’s occupation in a private university, and living arrangement in a private university. Conclusion: Factors influencing family planning decisions among students included cultural norms, religious beliefs, accessibility to contraceptives, and concerns about societal acceptance. Read more