Hepatocellular carcinoma (HCC) remains a leading cause of cancer-related mortality worldwide, with poor prognosis and limited treatment options, particularly in advanced stages. Glypican-3 (GPC3) has emerged as a promising therapeutic target, but existing antibodies primarily bind its C-terminal region, where glycosylation can mask epitopes and compromise efficacy. To address this limitation, we focused on the GPC3 N-terminal region, which offers better accessibility and potential for tumor signaling regulation. We developed Pro-12, a high-affinity humanized IgG1 antibody targeting the 25-45 peptide of the GPC3 N-terminus, avoiding glycosylation interference while modulating tumor pathways. Building on Pro-12, we engineered a GPC3/CD3 bispecific antibody (BsAb) using CrossMab and Knob-into-Hole technologies. This BsAb demonstrated dual anti-tumor effects by activating immune cells and inhibiting both the Wnt/β-catenin and PI3K/AKT pathways, achieving outcomes typically requiring tri-specific antibodies. Our findings highlight the GPC3 N-terminal region as a novel therapeutic target and introduce a promising bispecific antibody approach for the treatment of GPC3-positive HCC.