Red cell distribution width (RDW) measures the variance in size of circulating red blood cells and is a strong independent predictor of morbidity and mortality in cardiovascular disease and heart failure. Predictive power of RDW on mortality after continuous-flow left ventricular assist device (CF-LVAD) implantation remains largely unknown. Four hundred nine patients who underwent CF-LVAD implantation between April 2004 and December 2015 were retrospectively analyzed. The primary outcome of interest was 90 day mortality after CF-LVAD implantation. Median RDW before CF-LVAD implantation was 15.8%. Patients with elevated RDW (>15.8%) at baseline had significantly lower hemoglobin (10.6 ± 1.8 vs. 11.9 ± 2.1 mg/dl; p < 0.001), lower mean corpuscular volume (84.9 ± 7.7. vs. 88.7 ± 5.9; p < 0.001), higher blood urea nitrogen (BUN; 36.3 ± 21.8 vs. 30.1 ± 17.1; p < 0.001), lower albumin (3.4 ± 0.6 vs. 3.7 ± 0.5; p < 0.001), and higher total bilirubin levels (1.67 ± 2.21 vs. 1.29 ± 0.96). Red cell distribution width was independently predictive of 90 day mortality (odds ratio [OR], 1.16 for 1% increase; CI, 1.04–1.31; p = 0.010). Discriminatory power of RDW alone was comparable to model of end-stage liver disease excluding INR (MELD-Xi) and HeartMate II risk scores. Mechanical unloading with CF-LVAD was associated with a reduction in RDW levels. These findings suggest that RDW, a simple and inexpensive test available through routine complete blood count, can be successfully used for mortality risk assessment in CF-LVAD candidates.