Cardiorenal syndrome (CRS) is a condition in which there is a complex interrelationship between cardiovascular disease (CVD) and chronic kidney disease (CKD). Impairment of one organ could accelerate pathological processes in the other, which in turn accelerates the progression of failure of both. Although clinical studies hint at a specific bidirectional interaction between cardiovascular system and kidney, insight into the pathogenesis of CRS remains unknown. One possible factor that could explain this link is endothelial dysfunction (ED). ED is not only involved in initiation and progression of atherosclerosis, but also contributes to progression of renal injury. Asymmetric dimethylarginine (ADMA) is an endogenous NO synthase inhibitor found in the plasma and cells. Plasma ADMA levels are increased in CKD patients and known to be an independent biomarker and predictor for future cardiovascular events as well as the progression of CKD. These findings indicate that accumulated ADMA-mediated ED may play important roles in CRS in CKD patients. In this review, we discuss the roles of ADMA in the development of ED, especially focusing on its roles in CRS.