Behavioral risk factors in adolescents make them vulnerable to human immunodeficiency virus (HIV). Although it is dissimilar to adults, adolescent HIV is less studied. This study aimed to determine various socio-demographic attributes and transmission dynamics associated with adolescent HIV in order to comment on how they differ from the overall epidemiology of HIV. A record-based, comparative study was conducted using data from adolescents (ALHIV) and adults registered in all HIV centers across the Indian state of West Bengal over four years. The socio-demographic profile and modes of HIV transmission were studied. Transmission dynamics were compared between adolescent and non-adolescent beneficiaries, as well as male and female HIV-positive adolescents. The association of adolescent HIV burden with child marriage and adolescent pregnancy rates was also tested. More than 50% of AL-HIVs were students. While heterosexuality (87.17%) was the commonest route of HIV transmission in adults, parent-to-child transmission (PTCT) (51.69%) and blood transfusions (12.86%) were major routes in AL-HIVs; also, they were significantly more prone to get infected through these routes. PTCT was significantly lower, and transmission by needle syringes was higher in male adolescents than in their female counterparts. Districts with a higher prevalence of child marriage and adolescent pregnancy had a significantly higher burden of AL-HIV. The transmission dynamics of adolescent HIV are largely different from those of adults, with PTCT and sociocultural issues playing significant roles. It is, therefore, essential to design targeted interventions to tackle the unique challenges of HIV in adolescents for more effective and comprehensive campaigns against the pandemic.