Purpose: The aim of this study was to analyze associations between serum cancer antigen 125 (CA 125) levels and left ventricular (LV) function in patients with end-stage renal disease on maintenance hemodialysis (HD). Methods: CA 125 levels, pro-brain natriuretic peptide (pro-BNP) and biochemical parameters were measured, and echocardiography was performed for 110 patients and 47 healthy controls. Results: The mean CA 125 level in patients, 38.78 AE 35.48 U/ mL, was significantly higher than that found in healthy controls (9.20 AE 4.55 U/mL; p ¼ 0.003). Patients with elevated CA 125 levels (n ¼ 40) had significantly lower levels of albumin and reduced relative wall thickness, LV ejection fraction (EF) and fractional shortening but significantly higher levels of pro-BNP and a greater left ventricular end-diastolic diameter (LVEDd) and -systolic diameter (LVESd). CA 125 levels were positively correlated with pro-BNP (r ¼ 0.596, p50.05) and C-reactive protein (CRP) levels (r ¼ 0.439, p50.05), as well as LVEDd (r ¼ 0.599, p50.001), LVESd (r ¼ 0.750, p50.001) and LV mass index (r ¼ 0.378, p50.05). In contrast, serum CA 125 levels were negatively correlated with albumin (r ¼ À0.513, p50.05) and hemoglobin (r ¼ À0.475, p50.05) as well as the EF (r ¼ À0.878, p50.0001). A depressed EF ( ¼ À1.121, p50.0001) and increased CRP levels ( ¼ 0.247, p ¼ 0.035) were independent predictors of high CA 125 levels in the whole group in the multivariate-model. Conclusions: Our study is the first to demonstrate an association between serum CA 125 levels and LV systolic dysfunction via inflammation in patients on maintenance HD.