Conflicting results for circulating glypican-3 (GPC3) were reported in hepatocellular carcinoma (HCC) diagnosis. We aimed to improve the diagnostic power of GPC3 by developing a GPC-HCC model for diagnosing HCC. GPC3 was tested for HCC (138), liver cirrhosis (56), and fibrosis (62) patients by ELISA. Data from patient groups were retrospectively analyzed. A novel score, GPC-HCC, based on combination of GPC3 and routine laboratory tests, was developed for HCC diagnosis. The GPC-HCC model values produced a significant 1.7-fold increase in liver cirrhosis and 3.2-fold increase in HCC, in comparison with liver fibrosis. In contrast to GPC3 and alpha fetoprotein (AFP), the GPC-HCC model showed high HCC diagnostic power with area under the curve (AUC) of 0.939, sensitivity 93 %, specificity 93 %, positive predictive value 89 %, negative predictive value 95 %, and efficiency 93 %. GPC-HCC AUC in HCC with single tumor, absent vascular invasion, and tumor size ≤3 cm were 0.93, 0.92, and 0.92, respectively, compared with 0.63, 0.63, and 0.64, respectively, for GPC3 and 0.69, 0.70, 0.55, respectively, for AFP. In conclusion, owing to these promising findings, the combination of GPC3 with other laboratory simple routine tests (GPC-HCC model) could improve the diagnostic power of GPC3 in HCC screening and follow up of cirrhotic patients.