Aim: We estimated the correlation between serum bilirubin concentrations and insulin resistance in advanced maternal age without diabetes mellitus. Method: The cross-sectional study involved consecutive 50 women of advanced maternal age without diabetes mellitus, and insulin resistance (IR) was diagnosed according to the homeostatic model assessment insulin resistant (HOMA-IR) formula and the cut-off point was set to more than 2.5. Serum bilirubin and HOMA-IR were compared between the IR (+) and IR (-) groups. Results: We found that serum bilirubin levels in the IR subjects were significantly decreased compared to those without IR (p = 0.0252). Serum bilirubin concentrations were negatively correlated with the weight and the fasting insulin concentrations in all subjects (r=−0.282, p=0.047, r=-0.424, p=0.002). Additionally, serum bilirubin had a negatively correlation with HOMA-IR (r = -0.410, p = 0.003) in all subjects. The multiple linear regression analysis found that serum total bilirubin levels were independently correlated with HOMA-IR (beta = -0.392, p= 0.015) in these subjects. Conclusions: The study demonstrated that serum bilirubin concentrations had negatively correlation with insulin resistance in advanced pregnant women without diabetes mellitus, and decreased serum bilirubin may forebode increased gestational diabetes mellitus risk in our study population.