: Klotho is a transmembrane protein with a wide spectrum of activity. The human Klotho gene shows 86% amino acid identity with the mouse protein. Many important pleiotropic functions of the Klotho protein have been revealed. Amongst them, there is a regulation of nitric oxide production, suppression of oxidative stress and inflammation, influence on the insulin-like growth factors and fibroblast growth factors signaling, modulation of calcium and phosphate metabolism, synthesis of vitamin D and other. Two forms of the Klotho protein are known. The secreted form strongly inhibits the oxidative stress, and, in humans, is more dominant than the membrane form. Studies on a mouse model resulted in the finding of the anti-aging effect of the Klotho protein. This activity is mainly associated with the suppression of oxidative stress, as well as it could be related to neuroprotective, cardioprotective, and metabolic functions.It might be speculated that Klotho, regarded as a neuroprotective factor, may have therapeutical applications in the future in the treatment of demyelinating and neurodegenerative disorders, especially multiple sclerosis (MS) and Alzheimer's disease (AD). The Klotho through inhibition of oxidative stress possesses cardioprotective properties. Of note, one functional variant of Klotho is a risk factor for coronary disease as well as some nucleotide polymorphisms are associated with carotid arteriosclerosis. Moreover, the Klotho protein can inhibit Angiotensin II-induced cardiomyocyte hypertrophy. All those effects indicate that the Klotho protein may be useful in the therapy of heart failure and hypertension. Undoubtedly, metabolic disturbances play an important role in the pathogenesis of many neurodegenerative and cardiovascular diseases. The metabolic effects of the Klotho protein are strongly connected with its neuroprotective and cardioprotective activity. This protein affects adipogenesis, metabolism of glucose and lipids as well as calcium-phosphate system by influence on the activity of fibroblast growth factors (FGF19, FGF23, FGF21). Finally, it has been revealed that the Klotho protein has antitumor activity. Besides, the FGF-Klotho system may have a role in longevity and aging-related disorders.