Background and Aim of the Study: HIV/AIDS is best viewed as a major epidemic which poses serious challenges to mankind on a global scale. The aim of this study was to assess the HIV/AIDS-related knowledge among secondary school students in Bangladesh and investigate the association between secondary school students’ socio-demographic characteristics and their level of knowledge about HIV/AIDS. Methods: Following multistage random sampling technique, a total of 384 students aged 11-17 years were sampled from eight secondary schools and interviewed through a predesigned semi-structured questionnaire. Data analysis was done at three stages including descriptive statistics, bivariate analyses, and multivariate logistic regression. Results: The findings of the study revealed that more than half (55.26%) of the students were above 14 years of age and their ages ranged from 11 to 17 years. This study also found that around three-fourths of the students (75.78%) watched television. With regard to knowledge, this study demonstrated that around two-fifths of the students (36.98%) had very good knowledge about HIV/AIDS and their main sources of HIV/AIDS information were television, newspaper, radio, textbooks, and teachers. The bivariate results of the study indicated that students’ age, gender, type of school, household income, fathers’ and mothers’ literacy, and watching television were significantly associated with level of knowledge about HIV/AIDS. In addition, students’ age, mothers’ literacy, and watching television were found as the significant predictors of knowledge about HIV/AIDS. Watching television was documented as the best single predictor. Conclusion: The results of the study strengthen the assumption that there is an influence of students’ socio-demographic characteristics upon their knowledge about HIV/ AIDS. Moreover, this study suggests that more information on HIV/AIDS should be included in the textbooks of secondary school students in Bangladesh to enhance their knowledge about the taboo subject.