The prevalence of premarital pregnancy among adolescents in Malaysia is alarmingly on the rise. In finding ways to curb this, it is important toexplore on their reproductive health knowledge. Although knowledge alone will not influence adolescent’s behaviour, it is one of the most important factors that affect their reproductive health. The study aimed to assess the reproductive health knowledge of premarital pregnant adolescents in adolescent rehabilitation centres in Malaysia and the associated factors. A cross-sectional study involving premarital pregnant adolescents staying in adolescent rehabilitation centres in three states (Kelantan, Johor and Penang) was conducted for one month. Thirty-three eligible adolescents participated through a self-administered validated questionnaire which assessed their knowledge on reproductive organs, sexual activity and pregnancy, contraception and complications of sexual activity.Majority of participants scored well in terms of correct responses in reproductive organs, sexual activity and pregnancy as well as complications of sexual activity. However, they obtained the least correct responses in contraception as evidenced by these responses: having a hot shower after sexual intercourse prevents pregnancy (30.3%) and vaginal washing after sexual intercourse prevents pregnancy (33.3%). Their main source of information on reproductive health was from mass media (72.7%), and eighty two percent participants were not willing to discuss about sex with their parents. A multiple linear regression analysis showed that the mean knowledge score was significantly influenced by four factors namely age at first coitus, history of rape, age of partner at first coitus of the girl and watching pornography. The premarital pregnant adolescents have good knowledge on reproductive health except on pregnancy prevention. The information taken from mass media has failed to equip them with the correct knowledge on contraception. This warrants the need to adjust the current reproductive health education to be more children-and adolescent-friendly so it can be the point of reference in the future