Hyperinsulinemia and the metabolic syndrome confer increased risks of endometrial carcinoma. The roles of insulin, and, insulin-like growth factor-binding proteins (IGFBPs) in the etiology of endometrial carcinoma, remain unclear. We recruited 206 patients with endometrial carcinoma and 350 healthy women to a case–control study of fasting insulin and IGFBP-related protein 1 (IGFBP-rP1) in a Chinese tertiary centre. Patients with endometrial carcinoma had higher insulin concentrations (14.8 ± 16.7 vs. 8.1 ± 9.4 μU/mL; p < 0.001) and lower IGFBP-rP1 levels (17.5 ± 17.2 vs. 22.4 ± 22.8 μg/L; p = 0.018) than controls. High insulin and IGFBP-rP1 levels were both positively and negatively associated with endometrial cancer (odds ratio for the highest tertile versus the lowest tertile: insulin: 4.11; 95% CI = 2.61–6.47; IGFBP-rP1: 0.38; 95% CI = 0.24–0.60). Logistic regression analysis confirmed the associations between endometrial carcinoma and fasting insulin or IGFBP-rP1 after adjustments for age, BMI, serum glucose, cholesterol, triglycerides and high-density lipoprotein cholesterol (odds ratio for the highest tertile versus the lowest tertile: insulin: 2.13; 95% CI = 1.30–3.49; IGFBP-rP1: 0.57; 95% CI = 0.34–0.94). Hyperinsulinemia and high IGFBP-rP1 levels confer altered risks for endometrial carcinoma.