In response to a fentanyl-driven overdose crisis, low-threshold supervised consumption sites, termed overdose prevention sites (OPS), have been rapidly implemented in Vancouver, Canada. Since approximately 88% of fatal overdoses in the province occur indoors, OPS have been integrated into select non-profit-operated single room accommodations (SRA) housing. We examined the social-structural features of these housing-based OPS (HOPS) on women's overdose risk.Ethnographic research was conducted from May 2017 to December 2018 in Vancouver. Data included 35 in-depth interviews with women who use drugs living in SRAs and approximately 100 h of observational fieldwork in SRAs and surrounding areas. Data were analyzed using an intersectional risk environment approach, with attention to equity and violence.Findings demonstrate that the social and structural environments of HOPS created barriers for women to access these interventions, resulting in an increased overdose risk. Primary barriers included uncertainty as to who else was accessing HOPS, rules prohibiting smoking, and a lack of trust in staff's abilities to effectively respond to an overdose. Most participants considered HOPS to be unsafe environments, and expressed fear of violence from residents and/or guests. The perceived risk of violence was informed by previous experiences of assault and the witnessing of violence. Many participants thus consumed drugs alone in their rooms to better control their safety, despite heightened overdose risk. Further, most participants did not perceive themselves to be at risk of an overdose due to drug use practices and tolerance levels, and viewed using alone as a safer option than HOPS.Findings highlight how the low-barrier design and operation of HOPS can undermine women's engagement with HOPS. Overdose prevention strategies in SRAs should also include gender-specific models (e.g. women-only HOPS, women peer workers) to help mitigate barriers to these services within the context of the current overdose crisis.