A major function of E-cadherin is the maintenance of cell adhesion and tissue integrity. E-cadherin deficiency in tumors leads to changes in cell morphology and motility. Protein kinase D1 (PKD1), a serine/threonine-specific kinase plays a role in multiple cellular processes including apoptosis, cytoskeleton remodeling, and invasion. We previously reported co-localization of protein kinase-D1 (PKD1) with E-cadherin at cell junctions in prostate cancer (PC) cells and demonstrated dysregulation of both PKD1 and E-cadherin in prostate tumors. In this study we investigated the functional consequences of PKD1 and E-cadherin down or upregulation in a panel of human prostate cancer cell lines. Cells with variable levels of PKD1 and E-cadherin expression were either transfected with siRNAs directed against PKD1 or E-cadherin or the expression of PKD1 or E-cadherin was upregulated by transfection of wild type PKD1 or E-cadherin and analyzed for oncogenic events such as cell proliferation, anchorage independent growth and invasion. The effectiveness of PKD1 and E-cadherin suppression/overexpression was confirmed by Western blot analysis. Knockdown of PKD1 and E-cadherin was associated with enhanced prostate cancer cell growth, colony formation, and cell invasion. Cell proliferation marker (Proliferating Cell Nuclear Antigen, PCNA) expression showed correlation with the growth of cells. Loss of either PKD1 or E-cadherin expression was associated with elevated expression of survivin, β-catenin, cyclin-D and c-myc. Ectopic expression of PKD1 and E-cadherin in PC cell lines resulted in decreased cell growth which was associated with increased caspase-3, decreased colony formation, and cell invasion. The malignant phenotype caused by knockdown of PKD1 and E-cadherin was rescued by suppression of β-catenin in PC cells. Our study demonstrates that combined dysregulation of PKD1 and E-cadherin contributes to the malignant phenotype of PC cells by influencing cell proliferation, motility and invasion. The effect of cell proliferation could be rescued by ß-catenin suggesting an important role of ß-catenin in PKD1/E-cadherin mediated effects.