Background: Diabetes mellitus and thyroid dysfunction are strongly related conditions. Thyroid problems are more common in people with diabetes mellitus, according to several researches. Thyroid dysfunction may have a negative impact on metabolic regulation and increase the risk of cardiovascular illnesses in a situation where they are already predisposed.. So, the work aims to evaluate the prevalence of thyroid dysfunction in prediabetic patients and to correlate thyroid abnormalities with cardiovascular risk. Patients and Methods: This case-control study was conducted in an outpatient clinic, Faculty of Medicine, Zagazig University, on 100 cases during the period from March 2023 to September 2023. They were classified into two groups: Group (A): 50 apparently healthy individuals as the control group. Group (B): 50 confirmed prediabetic cases. Results: Group B had significantly higher glycemic parameters and triglyceride (TG) than group A while lower high-density lipoprotein (HDL-c). It was found that the prevalence of thyroid dysfunction in group B was 16% as 8% have a subclinical hypothyroidism (SH), 4% have a goiter, and 4% have Hashimoto's thyroiditis while controls in group A were normal. Thyroid hormones and antibodies were significantly higher in group B than group A, P<0.001. Electrocardiogram (ECG) shows 12% of the group (B) have ischemic changes and 4% have sinus tachycardia. Left ventricular ejection fraction (LVEF) was significantly lower in prediabetic, P=0.02 and Framingham's score was significantly higher in prediabetic, P<0.001. Conclusion: Patients with prediabetes have increased prevalence of thyroid dysfunction mainly SH and they are at higher cardiovascular risk than normal population.