Aim: Vitamin D deficiency, which is prevalent among young women in Middle Eastern populations, has been linked to cardiovascular disease. Epicardial adipose tissue (EAT) has also been found to be associated with coronary artery disease. However, data on the relationship between vitamin D status and epicardial adiposity is limited. This study aims to investigate the effect of vitamin D deficiency and replacement therapy on EAT thickness in healthy, young premenopausal women. Methods: Thirty-one premenopausal women with vitamin D deficiency and 31 age-matched women with normal vitamin D levels were enrolled in this study. EAT thickness was measured echocardiographically. Measurements were performed at baseline in both groups and were repeated at the 6-month follow-up in vitamin D deficient subjects after vitamin D replacement therapy. Results: The baseline plasma 25-hydroxyvitamin D levels were lower in the vitamin D deficient group compared to the control group and were significantly improved following replacement therapy. EAT thickness was significantly higher in the vitamin D deficient group, and no significant change occurred following replacement therapy. In the linear regression analysis, waist circumference (β= 0.031 [0.005-0.057], p=0.020) and 25(OH)D level (β=-0.020 [(-0.028)-(-0.013)], p<0.001) independently correlated with EAT thickness. Conclusion: Vitamin D deficiency is associated with a significant increase in EAT thickness in premenopausal women; however, a net beneficial response to adequate replacement therapy was not observed during the short period of therapy during our study. Longer periods of replacement therapy and follow-up may be useful to demonstrate the potential beneficial effects of vitamin D replacement on epicardial adiposity.