Introduction: Social-structural inequities impede access to, and retention in, HIV care among structurally vulnerable people living with HIV (PLHIV) who use drugs. The resulting disparities in HIV-related outcomes among PLHIV who use drugs pose barriers to the optimization of HIV treatment as prevention (TasP) initiatives. We undertook this study to examine engagement with, and impacts of, an integrated HIV care services model tailored to the needs of PLHIV who use drugs in Vancouver, Canada - a setting with a community-wide TasP initiative. Methods: We conducted qualitative interviews with 30 PLHIV who use drugs recruited from the Dr. Peter Centre, an HIV care facility operating under an integrated services model and harm reduction approach. We employed novel analytical techniques to analyse participants' service trajectories within this facility to understand how this HIV service environment influences access to, and retention in, HIV care among structurally vulnerable PLHIV who use drugs. Results: Our findings demonstrate that participants' structural vulnerability shaped their engagement with the HIV care facility that provided access to resources that facilitated retention in HIV care and antiretroviral treatment adherence. Additionally, the integrated service environment helped reduce burdens associated with living in extreme poverty by meeting participants' subsistence (e.g. food, shelter) needs. Moreover, access to multiple supports created a structured environment in which participants could develop routine service use patterns and have prolonged engagement with supportive care services. Our findings demonstrate that low-barrier service models can mitigate social and structural barriers to HIV care and complement TasP initiatives for PLHIV who use drugs. Conclusions: These findings highlight the critical role of integrated service models in promoting access to health and support services for structurally vulnerable PLHIV. Complementing structural interventions with integrated service models that are tailored to the needs of structurally vulnerable PLHIV who use drugs will be pursuant to the goals of TasP.