Background: Obesity is an independent risk factor of the metabolic syndrome and it is highly associated with the onset of diabetes mellitus. Obesity is a worldwide epidemic that is intimately linked to a number of health issues, including metabolic disorders, diabetes mellitus, and cardiovascular disease. Diabetes is a chronic metabolic disorder with multiple causes. It is characterized by irregularities in insulin secretion, function, or both, resulting in chronically high blood glucose levels. Type 2 diabetes mellitus accounts for ninety to ninety-five percent of cases, surpassing the prevalence of type 1 diabetes mellitus. The primary hereditary factors are insulin action resistance and inadequate compensatory insulin production. Vitamin D is significant in metabolism, particularly in regulating glucose homeostasis. According to recent research, a vitamin D deficiency can inhibit insulin production and increase the onset of insulin resistance. Low blood levels of vitamin D have been linked to hyperinsulinemia and impaired glucose tolerance, which frequently come on by obesity and significantly increase the risk of developing diabetes mellitus. The objective of the current review is to highlight the relationship between obesity, the development of type 2 diabetes, and vitamin D level in the body.