Carnosine (β-alanyl-l-histidine) is an endogenously synthesized dipeptide that is present in different human tissues, e.g. in the kidney. Carnosine is hydrolyzed by the enzyme carnosinase. There are two carnosinase homologs: serum-secreted carnosinase and nonspecific cytosolic dipeptidase, encoding by gen CNDP1 and CNDP2, respectively, and located on chromosome 18q22.3. Carnosine is engaged in different metabolic pathways in the kidney. Carnosine functions as a radical species of oxygen scavenger and a natural angiotensin converting enzyme inhibitor. It reduces the level of proinflammatory and profibrotic cytokines, inhibits advanced glycation end products formation as well as it decreases the mesangial cell proliferation. This chapter will present the results of studies concerning the role of carnosine in kidney diseases, particularly in ischemia/reperfusion-induced acute renal failure, diabetic nephropathy, gentamicin- and cisplatin-induced nephrotoxicity and also in blood-pressure regulation. The correlations between serum carnosine concentration and serum carnosinase activity and polymorphism in the CNDP1 gene were analyzed. The role of CNDP1 gene polymorphism in the development of diabetic nephropathy and nondiabetic chronic kidney disease is discussed. Carnosine has nephroprotective properties. Further studies of carnosine role in kidney may offer therapeutic perspectives in renal diseases.