Abstract Background and Aims Hypothyroidism is the most common disease of the thyroid gland. Thyroid hormone plays a crucial role in regulating tissue growth and metabolism. Additionally, patients with thyroid dysfunction have a higher incidence of caries and periodontal problems. The presence of calcium and phosphate ions seems to be effective in remineralizing teeth and reducing caries. The aim of this study was to evaluate the salivary level of calcium in patients with hypothyroidism. Results The results of this study showed that saliva calcium concentration in patients with hypothyroidism is significantly lower than healthy subjects. Also, no significant association was found between salivary calcium levels and TSH and T4 hormones level of blood. Conclusion The increased prevalence of dental caries in patients with hypothyroidism may be related to a decrease in their calcium levels.