Abstract: Objective To investigate the relationship between the expression of miRNA-15a-5p in peripheral blood leukocytes of polycystic ovary syndrome (PCOS) patients and PCOS. Methods The expression of miRNA-15a-5p in peripheral blood leukocytes of PCOS patients was detected by qRT-PCR. The correlation between miRNA-15a-5p and a series of variables were analyzed by Pearson or Spearman rank analysis. Results The PCOS group showed significant higher levels of miRNA-15a-5p than the healthy control group. After correction of age and BMI, the level of miRNA-15a-5p in the PCOS group was positively correlated with waist circumference (WC), homeostasis model assessment of insulin resistance (HOMA-IR), fasting insulin (FINS), fasting blood glucose (FBG) and 2-hour blood glucose (2hBG). MiRNA-15a-5p is an independent influencing factor of PCOS. According to ROC curve analysis, miRNA-15a-5p could be a potential diagnostic biomarker of PCOS. Conclusions MiRNA-15a-5p is associated with PCOS. MiRNA-15a-5p may involve the pathogenesis of PCOS through insulin resistance. MiRNA-15a-5p can be used as a potential molecular marker in the early stage of glucose metabolism disorder in PCOS patients.