Teenagers face challenges due to the lack of information about sex, sexuality, body changes, puberty, teenage pregnancy, early childbearing, HIV/AIDS in most developing countries, and Bangladesh is no exception. However, the study aims to explore the contributing factors of inadequate sex education at schools in Bangladesh. The study reviewed a variety of secondary sources and literatures to understand the contributing factors of inadequate sex education and analyzes those data and literatures. Therefore, the study found that there is a lack of a comprehensive sex education policy and formal sex education is very limited in Bangladesh. Moreover, it also found that there are very few chapters about sex education in the biological book, but teachers feel uncomfortable teaching about these topics. Furthermore, the parents are not confident to talk with their children as they have insufficient knowledge about sex education topics. In addition, the cultural and religious barriers are also responsible for inadequate sex education due to the orthodox thoughts of the family and society. The paper recommends that there should have a comprehensive sex education policy, and curriculum. Moreover, the focus should be on the implementation of interventions for the teachers' training, parent’s session, & community engagement programs. Keywords: Adolescent, Sex education, Parent’s attitude, Teachers’ perception, Bangladesh