This study investigates the social and structural drivers shaping HIV risk among high-risk populations (HRGs)Injecting Drug Users (IDUs) and Female Sex Workers (FSWs) in Aizawl City, Mizoram, the epicentre of Indias HIV epidemic. While behavioural factors remain important, the research emphasizes the wider social, economic, and spatial conditions that frame vulnerability and constrain prevention efforts. A cross-sectional descriptive study was conducted among 354 IDUs and 22 FSWs during 2021 through Targeted Intervention (TI) programmes using a semi-structured questionnaire. Data were analyzed through both descriptive statistics and thematic interpretation to understand the intersection of structural and behavioural risk factors. Findings reveal that HIV vulnerability in Aizawl is deeply embedded in socioeconomic marginalization, housing instability, and limited access to harm reduction services. IDUs are predominantly young males engaged in poly-substance use and risky injecting practices driven by withdrawal symptoms, syringe scarcity, and fear of policing. FSWs, mostly young and married, face heightened HIV prevalence due to inconsistent condom use, economic dependency, and concealed sex work within domestic spaces. Structural constraints such as criminalization, stigma, and spatial exclusion, particularly in neighborhoods like Dawrpui and Venghlui, create spaces of risk that perpetuate the epidemic.The study underscores the need for spatially sensitive interventions that integrate social protection, harm reduction, and gender-responsive approaches into HIV prevention strategies in Mizoram.