Notch signaling pathway regulates cancer cell growth. RBPJ is a key transcription factor downstream of Notch receptor activation, whereas the role of RBPJ in carcinogenesis of prostate cancer is ill-defined. Here, we evaluated the effects of RBPJ inhibition on the growth of prostate cancer cells. We knocked down RBPJ in prostate cancer cells by a short hairpin interfering RNA (shRNA). We measured cell growth by an MTT assay. We analyzed the levels of cell-cycle-associated proteins by Western blot. We found that shRNA for RBPJ efficiently inhibited RBPJ expression in prostate cancer cells, resulting in a significant decrease in the cell growth. Further, RBPJ-mediated cell-growth inhibition appeared to be resulting from alteration of cell-cycle inhibitors p21 and p27, cell-cycle activators CDK2, CDK4 and CyclinD1, and apoptosis-suppressor Bcl-2. Our data suggest that shRNA intervention of RBPJ expression could be a promising therapeutic approach for treating human prostate cancer.