Mesenchymal stem cells(MSCs) have the potential to self-replicate, proliferate and differentiate into chondrocytes, adipocytes, osteocytes and myocytes. Recent studies indicate that vitamin K2 plays a role in bone metabolism. But the mechanism is still unclear. We evaluated effect of vitamin K2 on osteogenesis and adipogenesis of MSCs from umbilical cord blood(UCB). By exposing MSCs to osteogenic and adipogenic medium with and without vitamin K2, the effects of vitamin K2 were analyzed. The results showed that vitamin K2 inhibits adipogenesis while at the same time it stimulates osteoblastic differentiation. These data are expected to provide novel information needed for successful therapeutic development for various types of osteoporosis and similar diseases related to bone formation.