We analyzed 832 single serum samples: collected at SVR12 in Cohort A and at HCC diagnosis in Cohort B. GPC-3 levels were significantly higher in patients with HCC compared to those without (95, 50–185 pg/mL vs. 48, 29–79 pg/mL; p < 0.001), with moderate diagnostic accuracy (AUC = 0.711). Here, GPC3 is linked to hepatocellular carcinoma.