We investigated the effects of CD34 + cell therapy on right ventricular (RV) function in patients with nonischemic dilated cardiomyopathy (DCM). We enrolled 60 patients with DCM who were randomized to CD34 + cell therapy (Stem Cells (SC) Group n = 30), or no cell therapy (Controls, n = 30). The SC Group received granulocyte-colony stimulating factor, and CD34 + cells were collected by apheresis and injected transendocardially. Patients were followed for 6 months. At baseline, the groups did not differ in age, gender, left ventricular ejection fraction, N-terminal probrain natriuretic peptide, or parameters of RV function. At 6 months, we found a significant improvement in RV function in the SC Group (tricuspid annular plane systolic excursion [TAPSE]: +0.44 ± 0.64 cm, p = .001; peak systolic tissue Doppler velocity of tricuspid annulus [St]: +1.5 ± 2.1 cm/s; p = .001; percent of fractional area change [FAC]: +8.6% ± 5%, p = .01), but not in Controls (TAPSE: -0.07 ± 0.32 cm, p = .40; St: -0.1 ± 1.2 cm/s; p = .44; FAC: -1.2% ± 3.2%, p = .50). On repeat electroanatomical mapping, we found an improvement in interventricular septum viability in 19 of 30 patients from the SC Group; this correlated with the improvements in RV function (13/19 in the improved septum group versus 3/11 in the remaining cohort, p = .029). These results suggest that patients with DCM, changes in RV function correlate with changes of viability of interventricular septum. CD34 + cell therapy appears to be associated with improved right ventricular function in this patient cohort. (Clinical Trial Registration Information: www.clinicaltrials.gov; NCT02248532). Stem Cells Translational Medicine 2018;7:168-172., (© 2018 The Authors Stem Cells Translational Medicine published by Wiley Periodicals, Inc. on behalf of AlphaMed Press.)