In the present investigation, the potential cytotoxic impact of catechin (Cat) combination therapy was examined, a highly polyphenolic compound extracted from black grapes (Vitis Vinifera L.), and Docetaxel (DTX) against prostate cancer cells (PC-3 cells) using Sulforhodamine B (SRB) assay. After extraction and characterization with HPLC chromatography, and evaluation of the Cat extraction, the IC₅₀ doses of treatment groups were identified in the PC-3 cell line: DTX therapy, Cat therapy, DTX + Cat treatment (1:1 volume), and untreated cells used as controls. The results show that the treatment with DTX, Cat, or their combination dramatically reduced the total number of PC-3 cells that survived. Also, the treatments induced DNA breakdown as indicated by DNA fragmentation assay causing clear cellular toxicity and apoptosis to the prostate cancer cells. The morphological changes seen after treatment with each drug alone were cell shrinkage, cell rounding, detaching, floating and obvious cell swelling and rupture indicating apoptotic features. Treatment with the combination of both compounds has shown more prominent rounded cells with more obvious apoptotic features than each treatment alone. In conclusion, Cat induced strong cellular cytotoxicity to prostate cancer cells, while it promotes the chemotherapeutic activity of DTX when administered in combination.