© 2018 The American Society of Transplantation and the American Society of Transplant Surgeons Patients with end-stage renal disease (ESRD) who are coinfected with hepatitis C virus (HCV) and human immunodeficiency virus (HIV) have access to effective treatment options for HCV infection. However, they also have access to HCV-infected kidneys, which historically afford shorter times to transplantation. Given the high waitlist mortality and rapid progression of liver fibrosis among coinfected kidney-only transplant candidates, identification of the optimal treatment strategy is paramount. Two strategies, treatment pre- and posttransplant, were compared using Monte Carlo microsimulation of 1 000 000 candidates. The microsimulation was stratified by liver fibrosis stage at waitlist addition and wait-time over a lifetime time horizon. Treatment posttransplant was consistently cost-saving as compared to treatment pretransplant due to the high cost of dialysis. Among patients with low fibrosis disease (F0-F1), treatment posttransplant also yielded higher life months (LM) and quality-adjusted life months (QALM), except among F1 candidates with wait times ≥ 18 months. For candidates with advanced liver disease (F2-F4), treatment pretransplant afforded more LM and QALM unless wait time was <18 months. Moreover, treatment pretransplant was cost-effective for F2 candidates with wait times >71 months and F3 candidates with wait times >18 months. Thus, optimal timing of HCV treatment differs based on liver disease severity and wait time, favoring pretransplant treatment when cirrhosis development prior to transplant seems likely.