Although the advent of highly active antiretroviral therapies has increased survival rates for many individuals living with HIV/AIDS, chronically homeless individuals with the disease continue to experience poor clinical outcomes and high mortality rates in comparison to the general population living with HIV. Housing as a structural intervention for homeless people living with HIV/AIDS has been shown both to be feasible and to improve access to care. However, few studies report the impact of accessing stable housing on residents' viral load counts, even though viral load has been accepted as the best predictor of clinical prognosis for over a decade. The Open Door is a nonprofit agency that utilizes a harm reduction, housing first model of care to improve clinical outcomes for homeless people living with HIV. This article describes the first study that utilizes viral load to assess the effectiveness of a housing first approach. During the study period, we found that 69% of residents of The Open Door achieved undetectable viral loads, which far exceeds adherence rates ranging from 13 to 32% that were found in other studies of similar vulnerable populations. This finding supports the feasibility of this approach and its potential impact on reducing HIV morbidity, mortality, and secondary transmission. Given that the majority of the residents were active substance users during the study period and achieved undetectable viral loads, our findings also substantiate other studies demonstrating that substance users are able to maintain clinical adherence.