AbstractGlypican‐3 (GPC3), a membrane‐associated heparan sulfate proteoglycan, is frequently upregulated in hepatocellular carcinoma (HCC). Yes‐associated protein (YAP) is also found over‐expressed in HCC and has been identified as a key effector molecule in Hippo pathway, which could control the organ size in animals through the regulation of cell proliferation and apoptosis and plays an important role in the development of malignant tumors. Studies have reported that GPC3 and YAP might collaborate to regulate the development of HCC. To elucidate the role of GPC3 in the development of HCC and its relationship with YAP, siRNA technique was employed to knock down GPC3 in Huh7 HCC cells. Moreover, recombinant human YAP‐1 was used to examine the effects of GPC3 on Huh7 cells. The results of flow cytometric analysis and Annexin‐V‐FLUOS apoptosis assay showed that knockdown of GPC3‐induced apoptosis in Huh7 cells, resulting in inhibition of cell proliferation as examined by EdU incorporation assay, migration, and invasion. GPC3 knockdown also suppressed the expression of YAP in mRNA and protein levels, as examined by fluorescence quantitative PCR and Western blot analysis. Moreover, addition of recombinant human YAP‐1 effectively rescued the cells from apoptosis triggered by GPC3 knockdown. Taken together, our findings suggest that GPC3 regulates HCC cell proliferation with the involvement of Hippo pathway. J. Cell. Biochem. 114: 625–631, 2013. © 2012 Wiley Periodicals, Inc.