Background: carbohydrate antigen 125 (CA125) is an increasingly promising biomarker of heart failure (HF), but its prognostic value in female patients with acute coronary syndrome (ACS) is unclear. We aimed to determine the short-term and mid-term prognostic value of CA125 serum levels in female ACS patients.Methods: A total of 131 consecutive female patients with ACS were retrospective enrolled. Their CA125 levels, B-type natriuretic peptide (BNP) levels and biochemical parameters were measured, and echocardiography was performed at admission. All-cause mortality during hospitalization and two-year follow-up was investigated for the prognosis.Results: The median value of CA125 serum level in the entire ACS patients was 13.85 U/mL. Patients in Killip Ⅲ had the highest values of CA125 level, followed by Killip Ⅱ and then Killip Ⅰ (p < 0.05). However, no statical difference was observed between Killip Ⅳ and Ⅰ-Ⅲ groups respectively (P > 0.05). The CA125 serum levels showed weak positive correlation with left ventricular end-diastolic diameter (LVEDD) (r = 0.3, P < 0.01) and a weak negative correlation with left ventricular ejection fraction (LVEF) (r = –0.23, p < 0.01). A receive operating characteristic (ROC) curve analysis showed that the AUC of CA125 in predicting acute heart failure (AHF) in ACS patients during hospitalization was 0.912, exhibiting higher sensitivity and specificity than BNP (0.846). The optimal cut-off value for CA125 in predicting AHF was 16.4 U/mL with a sensitivity of 0.916 and specificity of 0.893. The Kaplan-Meier survival analysis demonstrated that patients with high values of CA125 level had a poor overall survival than those with low values of CA125 level (log-rank, p < 0.001), whether during hospitalization or mid-term follow-up. Conclusion: Elevated CA125 level can be used to predict AHF in female ACS patients. Patients with elevated CA125 levels had higher mortality in short-term and mid-term than those with low CA125 levels.