Background and Aims: Several investigators have reported the significance of circulating galectin-3 in thyroid cancer patients. However, the precise meaning of circulating galectin-3 remains unclear. The aim of this study was to investigate the relationships between serum galectin-3 levels and angiogenetic factors, and nutritional and inflammatory indicators in patients with thyroid cancer. Materials and Methods: Sixty-one patients with thyroid tumors were enrolled, comprising 47 pre-treatment thyroid cancer patients and 14 patients with benign thyroid diseases. Galectin-3, interleukin (IL)-6, vascular endothelial growth factor, granulocyte colony-stimulating factor (G-CSF), soluble form of intercellular adhesion molecule-1 (sICAM-1), retinol binding protein, prealbumin, albumin, and transferrin were measured. C-reactive protein (CRP), neutrophil count, lymphocyte count, and neutrophil/lymphocyte ratio (NLR) were also investigated. Results: The amounts of circulating galectin-3 in benign disease and thyroid cancer were significantly higher than those of healthy volunteers (P < 0.001). Analysis of galectin-3 performance in distinguishing malignant disease from benign disease using a receiver operating characteristic curve revealed that the area under the curve was 0.555. There were statistically significant correlations between the circulating amount of galectin-3 and IL6, G-CSF, and sICAM-1. Serum galectin-3 showed statistically significant correlations with albumin, prealbumin, and transferrin. Circulating galectin-3 exhibited strong correlations with CRP, neutrophil count, lymphocyte count, and NLR. Conclusions: Galectin-3 may be one of the key factors in the regulation of angiogenesis, inflammation, and nutrition.