Cardiovascular Diseases (CVD) is considered as the leading cause of health problems that influence the life of the people. Indians are more vulnerable to have coronary artery disease (CAD) in young age group with a prevalence of 5-10%. It is well known that vitamin D insufficiency, or deficiency, is highly prevalent in the general population. Peripheral arterial disorders are reported to be associated with low serum vitamin D levels. A growing amount of data has highlighted the potential link between vitamin D and major cardiovascular risk factors, such as diabetes, hypertension, and chronic kidney disease. Aim: To assess the serum levels of 25(OH) vitamin D in patients with Acute ST Elevation Myocardial Infarction (STEMI) in young patients (aged ≤ 45 years). Material and Methods: It was an observational age and sex matched case-control study conducted at PT. B.D. Sharma Post Graduate Institute of Medical Sciences (PGIMS), Rohtak, in the Department of Cardiology for 12 months after the approval from ethical committee of PGIMS Rohtak. A total of 100 patients (50 case and 50 controls) were selected. Results: A statistically significant correlation of hypovitaminosis D in the patients with age less than 45 years with acute myocardial infarction was observed. Most of patients who were admitted with acute MI had subnormal vitamin D levels. Statistically significant association was observed between vitamin D Level and case group (p<0.001). Participants in case group were having significantly higher vitamin D deficiency. There was significantly higher vitamin-D deficiency in age group of 36-45 years when compared to age group of 26-35 years among case group (p value < 0.001). Conclusion: In present study, vitamin D insufficiency was found in most of the patients with acute myocardial infarction and was linked to many of its risk variables. Hypovitaminosis D is associated with other cardiovascular risk factors including hypertension, diabetes, obesity, metabolic syndrome and dyslipidaemia. The present study was proposed to assess the 25(OH) vitamin D status with acute ST elevation myocardial infarction in young patients of age less than 45 years and revealed that serum 25(OH) vitamin D levels were significantly lower in the cases of acute myocardial infarction when compared to the control population. To prevent cardiovascular problems, this highly frequent vitamin D deficiency should be screened and treated adequately. The clinical analysis has shown that vitamin D deficiency is having a significant adverse impact on the cardiac function and blood pressure in AMI. Moreover, the vitamin D is exerting biological effects on cardiac myocytes, by stimulating calcium-ATPase activity and calcium uptake in cardiac myocytes