Human histone lysine demethylases 4C is an AR co-regulator. We investigated the role of KDM4C in prostate cancer (PCa). Analysis of both Oncomine gene datasets and commercial tissues array, we observed that the mRNA and protein expression of KDM4C is highest in metastatic prostate cancer tissues. PCa patients with higher KDM4C expression level correlate to worse prognosis. Knockdown of KDM4C in PCa cells reduced cell proliferation, soft agar colony formation, migration, and invasion as well as suppressed tumor growth in PCa orthotopic model in nude mice. Prostate cancer stem cells and docetaxel resistant PCa cells express higher KDM4C proteins. Micro Western Array (MWA) is an antibody-based high throughput protein array allowing detecting protein expression level or phosphorylation status change of 96-192 different antibodies in 6 to 15 samples simultaneously. MWA analysis indicated that reduction of KDM4C affected protein expression of cell cycle regulatory proteins, cMyc, DKK3, and EMT marker proteins. Our study indicated that KDM4C is a novel oncogene in PCa and KDM4C may serve as a prognostic biomarker for clinical outcome of PCa.