Vitamin K is one of the fat-soluble vitamins with two natural types, phylloquinone (K1) and menaquinone (K2), and one synthetic form named menadione (vitamin K3). Vitamin K plays key roles in different physiological functions such as blood coagulation, bone metabolism, and the regulation of some enzyme systems. It can also act as a cofactor for some plasma proteins, thereby affecting immune and inflammatory responses particularly mediated by T cells. Studies have found links between vitamin K levels and diseases, including inflammatory diseases and cancer. However, there is limited information about how the immune and inflammatory responses can be influenced by vitamin K. Further studies are necessary to clarify the roles of vitamin K on the immune system.