Introduction In Noakhali and Lakshmipur, more adolescents are in school and community today than ever before; however, there are no studies that have assessed their comprehensive knowledge of HIV/AIDS. Thus, this study tried to assess the level of this knowledge and the factors associated with it among in-school and community level adolescents in Noakhali and Lakshmipur district.

Methods A cross-sectional school and community- based study was conducted using a facilitator-guided self-administered questionnaire conducted April 2016. The respondents were students attending regular school in 14 high schools and 70 community level adolescents located in 14 different Sub-districts in Noakhali and Lakshmipur district. The proportion of adolescents with comprehensive HIV/AIDS knowledge was computed and compared by sex. The investigating tool used was a prepared, pretested questionnaire. This had both open-and close-ended questions related to various aspects of HIV/AIDS. Different factors related to HIV/AIDS and information was gathered. The subjects were assessed for knowledge of various aspects of HIV/AIDS and associated risk factors. It was subsequently followed by an open discussion on HIV/AIDS with the students. The factors that were associated with the comprehensive HIV/AIDS knowledge were assessed using multivariable logistic regression.

Results Only about one in four, 677 (24.5%), in-school adolescents and community level adolescents have comprehensive HIV/AIDS knowledge. The knowledge was better among in-school adolescents from families with a relatively middle or high wealth index (adjusted OR [95% CI]=1.39 [1.03–1.87] and 1.75 [1.24–2.48], respectively), who got HIV/AIDS information mainly from friends or mass media (adjusted OR [95% CI]=1.63 [1.17–2.27] and 1.55 [1.14–2.11], respectively) and who received education on HIV/AIDS and sexual matters at school (adjusted OR [95% CI]=1.59 [1.22–2.08]). The females were less likely to have comprehensive HIV/AIDS knowledge compared to males (adjusted OR and [95% CI]=0.60 [0.49–0.75]).

Conclusion In general, only about a quarter of in-school adolescents had comprehensive HIV/AIDS knowledge. Although the female adolescents are highly vulnerable to HIV infection and its effects, they were by far less likely to have comprehensive HIV/AIDS knowledge. HIV/AIDS information, education and communication activities need to be intensified in high schools and rural community.