The research work focuses on the causes of Premarital Sex among Secondary School Girls and Its Impact on their Academic Achievements in Ika North-East L.G.A of Delta State. One Hundred and Fifty Questionnaires were administered to female students in different schools. The data were analyzed and the following findings were discovered: Participation in Sex Education was at a low stage; Drop out cases were paramount in that vicinity; there is high rate of Media Exposure; Poverty level is also a causative factor; Peer Group Influence/Imitation; Single Parenting has its own implications; Home Environmental Factor; Early Marriage; Teenage Pregnancy; reading about Contraceptives as well as Watching/Reading Pornographic Films/Magazines has increased the negative appetite of these teenagers. The following recommendations were made: Premarital Sex should be discouraged among teenagers and school girls by Parents, Teachers, Guardians’, Religious Leaders, Counselors and Government. Parents/Guardians’ and Government should create awareness on the high risk involved in premarital sex such as contacting Sexually Transmitted Diseases, Early Marriage, Single Parenting, Academic Failure (Drop Out) and lots more, which are the negative impacts of Premarital Sex towards their life and Academic Success. Parents should discourage their children from watching pornographic films/Internet sites, reading pornographic magazines/write-ups and Family planning pamphlets. Government should provide adequate facilities to educate a Girl-Child at the early stage in life by emphasizing on Sex Education in their early Secondary School days and create an enabling environment that will improve life for the young ones. Empower Religious Leaders/Institutes in motivating the Children and distracting them from such negative vices to life. There should also be a proper service or facility that caters for Broken Homes, Pregnant Teenagers, Single/Separated Parents, Orphans and a proper investigation and monitoring of adopted children.