The relationship between vitamin D deficiency and idiopathic central precocious puberty (ICPP) has been recently documented. In this study, 280 girls diagnosed with ICPP and 188 normal puberty control girls of similar ages were enrolled and retrospectively studied. The ICPP group had significantly lower serum 25-hydroxyvitamin D (25[OH] D) levels than the control group. Furthermore, a nonlinear relationship was found between serum 25[OH] D and ICPP, and a cut-off point for serum 25[OH] D was found at 31.8 ng/ml for ICPP with and without adjusting the different confounding factors. Girls with serum 25[OH] D >= 31.8 ng/ml had a lower odds ratio (unadjusted: OR 0.36, 95% CI 0.15 to 0.83, P < 0.05; height and weight adjusted: OR 0.44, 95% CI 0.18 to 1.08, P = 0.072; BMI adjusted: OR 0.36, 95% CI 0.16 to 0.84, P < 0.05). The ICPP subjects with 25[OH] D deficiency had a higher body mass index (BMI) than the subjects from the two other subgroups. Correlation analysis showed that vitamin D level is correlated with BMI and some metabolic parameters in the ICPP group. Our study suggested that vitamin D status may be associated with ICPP risk and may have a threshold effect on ICPP.