Although red cell distribution width (RDW) has emerged as a biomarker of clinical prognostic value across a variety of clinical settings in the last two decades, limited evidence is available for its role in end-stage renal disease. We enrolled 313 incident patients undergoing continuous ambulatory peritoneal dialysis (CAPD) in this retrospective observational study from 2006 to 2015. In the fully adjusted model of Cox regression analysis, the adjusted hazard ratios for the high RDW group versus the low RDW group were 2.58 (95% confidence interval (CI) = 1.31-5.09, p = 0.006) and 3.48 (95% CI = 1.44-8.34, p = 0.006) for all-cause and cardiovascular disease (CVD)-related mortality, respectively. Based on area under the receiver operating characteristic curve (AUC) analysis, RDW (AUC = 0.699) had a stronger predictive value for all-cause and CVD-related mortality than other biological markers including hemoglobin (AUC = 0.51), ferritin (AUC = 0.584), iron saturation (AUC = 0.535), albumin (AUC = 0.683) and white blood cell count (AUC = 0.588). Given that RDW is a readily available hematological parameter without the need for additional cost, we suggest that it can be used as a valuable index to stratify the risk of mortality beyond a diagnosis of anemia.