Objective: Serum copper (Cu) is an essential trace element that plays a key role in thyroid hormone production. An inappropriate level of serum Cu might be related to development of both benign and malignant thyroid neoplasm. Nodular goiter and papillary thyroid carcinoma (PTC) are common benign and malignant tumors of the thyroid, respectively. This study aims to compare the serum Cu levels of healthy women with women with PTC or nodular goiter. Materials and Methods: A total of 205 Thai women were recruited for this cross-sectional study. The reference group was comprised of 100 healthy volunteers. There were 61 nodular goiter and 41 PTC patients that had been treated with surgery. Serum Cu was measured using an atomic absorption spectrophotometer and the three groups were compared. Results: The serum Cu levels of the PTC, nodular goiter and the reference group were 0.93 (0.85, 1.11) μg/ml, 1.03 (0.90, 1.14) μg/ml and 0.97 (0.80, 1.11) μg/ml, respectively. The results were not statistically different (P = 0.10). A post hoc subgroup analysis in the PTC group showed only serum Cu levels were significantly higher in the blood vessel invasion group (P = 0.02). Conclusion: The serum Cu levels of patients with PTC and nodular goiter were not different and did not differ significantly from the reference group. Despite related to with only one pattern of histopathologically aggressive PTCBlood vessel invasion, serum Cu levels cannot be used as an assistive tool for diagnosis and the prognosis of PTC.