OBJECTIVES: Injectable opioid agonist therapy (iOAT) has previously been demonstrated to be an effective treatment option for individuals with a severe opioid use disorder (OUD) who have been unsuccessful on first line therapy (eg, buprenorphine/naloxone or methadone). Many individuals with severe OUD may also have HIV infection. Despite this, no literature currently exists examining the relationship between antiretroviral therapy (ART) initiation and adherence following iOAT initiation in the outpatient setting. METHODS: Retrospective case series (n = 3) of HIV-infected individuals with a severe OUD who were refractory to oral opioid agonist treatment and were started on iOAT in a community setting in Vancouver, Canada. Outcomes of interest included: (1) iOAT induction and maintenance dosing schedules; (2) ART adherence demonstrated by change in HIV viral load. RESULTS: All 3 patients initiated and successfully reached iOAT maintenance doses with significant reduction in illicit opioid use. Stable iOAT was associated with increased ART initiation and adherence, and decreased HIV viral loads. Conversely, poor retention or discontinuation of iOAT was associated with reduced adherence to ART and in 1 patient, increased HIV viral loads. CONCLUSIONS: The individual cases presented suggest that among individuals with severe OUD and HIV infection, iOAT may improve HIV treatment uptake and retention in care.