Background: The effects of vitamin D on calcium homeostasis and bone metabolism have been investigated for many years. However, studies conducted in the last 20-25 years have shown that vitamin D has many functions beyond calcium metabolism. It is now known that vitamin D deficiency has a role in the formation of autoimmune diseases such as inflammatory bowel disease, rheumatoid arthritis, and multiple sclerosis and other diseases including diabetes, many types of cancer, and heart disease. The aim of this study was to compare the vitamin D levels of patients with Hashimoto’s thyroiditis and healthy subjects and to evaluate possible relationships between vitamin D and other parameters. Methods: This single-centre study was conducted at Izmir Bozyaka Training and Research Hospital. The participants (n=80) were divided into two groups with one group consisting of patients with the diagnosis of Hashimoto’s thyroiditis (patient group, n=40) and one group consisting of healthy volunteers (control group, n=40). The patient group and control group were compared in terms of vitamin D levels. Thyroid-stimulating hormone (TSH), free T3 (FT3), free T4 (FT4), anti-Tg, anti-TPO, age, and body mass index (BMI) were also measured and compared. Results: The mean vitamin D level was 18.0±3.0 ng/mL and the median vitamin D level was 16.7 ng/mL (6.5-41 ng/mL) in the control group. The mean vitamin D level was 16.1±7.6 ng/mL and the median vitamin D value was 14.85 ng/mL (0.18-35.50 ng/mL) in the patient group. There was no statistically significant difference between the two groups in terms of vitamin D levels (p=0.305). When Thyroid-stimulating hormone (TSH), free T3 (FT3), free T4 (FT4) and body mass index (BMI) were examined, once again, no statistical difference was found between the groups. In addition, no statistically significant positive or negative correlation was found between vitamin D level and any other parameters. Conclusion: Our study showed a numerical reduction in vitamin D levels between the patient and control groups; however, our data cannot evaluate potential relationships between vitamin D levels and Hashimoto’s thyroiditis.