The insulin-like growth factor (IGF) pathway is believed to play a pivotal role in thyroid carcinogenesis. Polymorphisms of IGF-1 and IGF binding protein-3 (IGFBP-3) have been associated with modulation of risk for the emergence of assorted common malignancies, but studies of the influence of such polymorphisms on risk of differentiated thyroid carcinoma (DTC) are lacking. In a case-control study of 173 DTC patients, 101 patients with benign thyroid disease, and 401 controls, an unconditional logistical regression model adjusted for age and sex was applied to calculate odds ratios (ORs) and 95% confidence intervals (CIs) for the associations between polymorphisms of IGF-1 and IGFBP-3 and DTC risk. IGFBP-3 rs2132572 GA/AA genotypes were associated with a decreased risk of DTC (adjusted OR = 0.6, 95% CI: 0.4-0.9), particularly multifocal DTC (adjusted OR = 0.3, 95% CI: 0.1-0.7). The association with DTC was more evident in subjects with a first-degree family history of cancer (adjusted OR = 0.4, 95% CI: 0.2-0.7, P(interaction) = 0.013) and non-drinkers (adjusted OR = 0.4, 95% CI: 0.2-0.7, P(interaction) = 0.028). A four single nucleotide polymorphism haplotype of IGFBP-3 was associated with a decreased risk of DTC (adjusted OR = 0.7, 95% CI: 0.5-1.0, P = 0.030). Our study suggests that polymorphic IGFBP-3 may be involved in susceptibility to DTC.