The cell therapy using tissue-engineered cartilage is essential because the surgical operation for the repair of defected cartilage is not sufficient. Mesenchymal stem cells(MSCs) are an ideal candidate for use in cell-based therapy because of their self-renewal ability and differentiation capability into specific cells such as chondrocytes. Especially, human umbilical cord blood(UCB) is an attractive cell source because it can be obtained easily and the process is noninvasive and painless. However, the life span of MSCs are limited and the accumulation of intracellular oxidative damage by aging causes the loss of differentiation capacity during ex vivo expansion. (-)-Epigallocatechin gallate(EGCG) is known as an anti-oxidant agent which has a role as a free radical scavenger. It can improve long-term cell viability. Therefore, differentiation capacity can be maintained. In this study, effects of EGCG on chondrogenic potential of UCB-MSCs were investigated. The proliferation and differentiation capacity of UCBMSCs was characterized during expansion. Optimal concentration of EGCG was decided. Addition of EGCG in the media increased the cell viability during chondrogenic induction. Glycosaminoglycan(GAG), a cartilage-specific extracellular matrix(ECM), was also increased. It was confirmed that EGCG could improve the chondrogenic potential of UCB-MSCs by reducing oxidative stress. These results can contribute to the repair of damaged articular cartilage using UCB-MSCs.