Prostate cancer is the most common malignancy in men and is the second leading cause of cancer-related mortality in developed countries. Recent work has revealed the significance of CIP-interacting zinc finger protein 1 (CIZ1) in cancer cell biology, but its roles in prostatic carcinoma are unknown. Our study compared CIZ1 gene expression in banked prostatic carcinomas versus matched paraneoplastic tissues and in tumor cell lines of varying origin. This study revealed that the expression of CIZ1 was higher in high-grade prostate cancer than in low-grade prostate cancer and normal tissues. Among the tumor cell lines, PC-3 exhibited the highest levels of CIZ1 expression. CIZ1 gene silencing in PC-3 cells reduced cell proliferation and colony formation, induced cell cycle arrest in G1, inhibited tumor formation in nude mice, and suppressed the expression of genes related to prostate carcinoma. These results suggest that CIZ1 may play an important role in the progression of human prostate carcinoma and us which may be used as a therapeutic target in prostate cancer.