Background: To investigate the prevalence of thyroid nodules (TNs) and to evaluate the association between TNs and metabolic syndrome (MetS) in the moderate iodine intake area of Jiangsu, China.Subjects and Methods: A cross-sectional study was carried out in a Chinese community-based epidemiological investigation from January to December 2014. A questionnaire was completed by 6494 subjects (2427 men and 4067 women). Thyroid ultrasound was performed by using a 7.5-MHz linear probe. MetS was defined according to the 2006 International Diabetes Federation criteria.Results: The prevalence of TNs in the study population was 17.7% (12.9% for men and 20.6% for women) and significantly higher in subjects with MetS [MetS(+)] than in those without MetS [MetS(-)] (25.8% vs. 15.5%, chi(2) = 78.471, P < 0.001). Binary logistic regression indicated that ( in addition to female sex and increased age) increased fasting plasma glucose (FPG), waist circumference (WC), hypertension, and smoking were positively associated with the prevalence of TNs.Conclusions: Our findings indicated a positive association between MetS and formation of TNs. Increased WC and FPG, as well as hypertension, might increase the prevalence of TNs.