Effect of anthropometric factors at adolescence and the change since young age on thyroid cancer risk is unclear. Here, we conducted a case-control study to investigate the association between anthropometric factors at the time of diagnosis and age 20 years and risk of thyroid cancer. A total of 173 patients with thyroid cancer (papillary carcinoma, n = 167 and follicular carcinoma, n = 6) and 865 age- and sex-matched controls were included. Anthropometric factors were assessed using a validated self-administered questionnaire and categorized into three groups. Odd ratios (ORs) with 95% confidence intervals (CIs) were estimated using conditional logistic models adjusted for potential confounders. Results showed a positive association between current weights, weight at age 20 years and height, and thyroid cancer risk. Adjusted ORs in the top tertiles were 2.46 (95% CI, 1.54-3.94; trend p \ 0.001) for current weight, 2.69 (95% CI, 1.71-4.25; trend p \ 0.001) for weight at age 20 years and 2.44 (95% CI, 1.52-3.93; trend p \ 0.001) for height compared with the lowest tertile. A positive association with current body surface area (BSA), BSA at age 20 years, and current body mass index was also observed, with respective adjusted ORs in the top tertile of 1.96 (95% CI, 1.23-3.11; trend p = 0.007), 1.82 (95% CI, 1.15-2.88; trend p = 0.007) and 1.71 (95% CI, 1.06-2.78; trend p = 0.034). In contrast, no association with risk was seen for a change in anthropometric factors since age 20 years. These findings suggested that body size in early life as well as in adult is associated with an increased risk of thyroid cancer.