IntroductionThe LINC‐II randomized controlled trial in St. Petersburg, Russia for HIV‐positive adults who inject drugs found that a multi‐component intervention including initiation of antiretroviral therapy (ART) during admission to an addiction hospital, strengths‐based case management and naltrexone significantly increased 12‐month HIV viral suppression and ART retention. We conducted a comparative cost analysis to determine if the 12‐month cost of the intervention is affordable within the current Russian health system.MethodsWe used LINC‐II trial records and questionnaire responses to calculate the resources utilized by each participant in the study, including inpatient days, medications, laboratory tests, outpatient consultations, case manager interactions and opioid medication treatment. Quantities of resources utilized were multiplied by unit costs for each resource estimated from the service fee or price lists used by the study facilities for each specific service delivered. We report the average cost/study primary (viral suppression at 12 months) or secondary (retention in care at 12 months) outcome/participant in 2021 USD and compare costs between study arms.ResultsThe trial enrolled 225 participants (111 intervention, 114 control) between September 2018 and December 2020. Viral suppression, non‐suppression and missing suppression results were 28% and 14%, 49% and 37%, and 31% and 41% for the control and intervention arms, respectively. Retention results were 35% and 51% for the control and intervention arms, respectively. The average cost per study participant was $2714 in the control arm and $4342 in the intervention arm. The average cost per participant virally suppressed at 12 months was $3662 (control) and $6355 (intervention). The average cost per participant retained at 12 months was $4050 (control) and $5448 (intervention). For those retained, the cost difference between the arms was comprised of opioid treatment (35%), case management (31%), outpatient visits (18%) and additional days of ART (12%).ConclusionsThe LINC‐II intervention increased the cost of care for HIV‐positive people who inject drugs in Russia significantly, but some components of the intervention, particularly earlier initiation of ART and case management, may be justifiable due to their success in reaching a challenging subgroup of the population in need.Clinical Trial NumberNCT03290391