The World Health Organization (WHO), defines sexual well-being as a multifaceted construct, consisting of more than absence of disease or experiences of pleasure. Further, the WHO suggests that sexual knowledge should contribute to sexual well-being. We examined the relationship between personal sexual knowledge-knowing one's individual sexual preferences-and sexual health knowledge-awareness of reproduction, contraception, and diseases-and sexual well-being, comprised of sexual satisfaction, assertiveness, and competence in a sample of 484 emerging adults. Personal sexual knowledge but not sexual health knowledge, was a significant predictor of sexual well-being. Further, this relationship was moderated by gender (stronger for women) but not prior sex education.