BACKGROUND: Many people who have a positive hepatitis C virus (HCV) antibody (Ab) test never receive a confirmatory HCV RNA viral load (VL) test. Reflex VL testing may help address this problem. We undertook a systematic review to evaluate the effectiveness of reflex VL testing compared with standard nonreflex approaches on outcomes across the HCV care cascade. METHODS: We searched 4 databases for studies that examined laboratory-based reflex or clinic-based reflex VL testing approaches, with or without a nonreflex comparator, and had data on the uptake of HCV RNA VL test and treatment initiation and turnaround time between Ab and VL testing. Both laboratory- and clinic-based reflex VL testing involve only a single clinic visit. Summary estimates were calculated using random-effects meta-analyses. RESULTS: Fifty-one studies were included (32 laboratory-based and 19 clinic-based reflex VL testing). Laboratory-based reflex VL testing increased HCV VL test uptake versus nonreflex testing (RR: 1.35; 95% CI: 1.16-1.58) and may improve linkage to care among people with a positive HCV RNA test (RR: 1.47; 95% CI: .81-2.67) and HCV treatment initiation (RR: 1.03; 95% CI: .46-2.32). The median time between Ab and VL test was <1 day for all laboratory-based reflex studies and 0-5 days for 13 clinic-based reflex testing. CONCLUSIONS: Laboratory-based and clinic-based HCV reflex VL testing increased uptake and reduced time to HCV VL testing and may increase HCV linkage to care. The World Health Organization now recommends reflex VL testing as an additional strategy to promote access to HCV VL testing and treatment. CLINICAL TRIALS REGISTRATION: PROSPERO CRD42021283822.