Aging is a complex biological process driven by a selective class of molecules and pathways that affect overall deterioration of physiological functions to increase the risk of age-related diseases. A role of vitamin D in mammalian aging is well documented. Since vitamin D has an essential role in bone formation and mineralization, its deficiency results in impaired bone mineralization, such as rickets in children, osteomalacia in adults and osteoporosis in the aged population. Vitamin D replacement therapy therefore is one of the most commonly prescribed treatments for the elderly. Recent studies using genetically altered mouse models, such as in Fgf-23(-/-) and klotho mutant mice, that exhibit altered mineral ion metabolism due to high vitamin D activities showed features of premature aging that include atherosclerosis, emphysema, osteopenia/osteoporosis, hypogonadism, soft tissue calcifications and generalized atrophy of organs; the pathologic effects of vitamin D in these mouse models are obvious, as diminution or genetic ablation of the vitamin D pathway ameliorated most of the above-mentioned phenotypes, by reversing mineral ion metabolism, and the resultant effect being prolonged survival of the mutant mice. These in vivo mouse studies, although subject to further molecular characterization, add new insights into the role of vitamin D in aging.