Abstract Background Opioid use is prevalent among people living with human immunodeficiency virus (HIV; PLWH) and adversely affects HIV outcomes. We assessed the effect of buprenorphine (BUP) initiation on subsequent HIV viral loads. Methods We identified PLWH from the Johns Hopkins HIV Clinical Cohort who initiated BUP between 2002 and 2017. Poisson regression with robust variance was used to estimate the prevalence of viral suppression (<200 copies/mL) before and after BUP initiation. We matched individuals who initiated BUP with controls based on viral load measurement dates and used prior event rate ratio (PERR) methods to estimate the effect of BUP initiation on viral suppression. PERR methods account for unmeasured confounders. Results We identified 279 PLWH who initiated BUP. After BUP initiation, PLWH were more likely to be virally suppressed (prevalence ratio PR, 1.19; 95% confidence interval CI, 1.03–1.37). After matching PLWH who initiated BUP to controls and accounting for measured and unmeasured confounders, BUP initiation increased viral suppression for both those on antiretroviral therapy (ART) at baseline (PERR PR, 1.08; 95% CI, 1.00–1.18) and those not on ART at baseline (PR, 1.31; 95% CI, 1.10–1.61). Conclusions Our results indicate that the initiation of BUP results in an increase in the probability of being virally suppressed after accounting for both measured and unmeasured confounders. Persons with opioid use disorder should initiate BUP to not only treat substance use but also to increase viral suppression allowing for treatment as prevention. Buprenorphine initiation was found to increase viral suppression among people living with human immunodeficiency virus (HIV; PLWH) with an opioid use disorder (OUD). Therefore, initiation is important to improve individual HIV outcomes among PWH with OUD and to reduce the risk of HIV transmission.