A B S T R A C TBackground: Right Ventricular (RV) functions are known to have an impact on determining the prognosis of patients with Non-Ischemic Dilated Cardiomyopathy (NICMP). Objectives: This study aimed to investigate the echocardiographic determinants of RV systolic dysfunction in patients with NICMP. Patients and Methods: This cross-sectional study was conducted on 79 patients with angiographically normal coronary arteries (mean age: 50.5 ± 12, mean Ejection Fraction (EF): 31 ± 4%) selected through purposive sampling The patients were divided into two groups based on their RV systolic function determined by tissue Doppler systolic velocities (RV-Sm): group A (RV-Sm ≥ 10 cm/s, N = 48) and group B (RV-Sm < 10 cm/s, N = 31). The two groups were compared regarding clinical, demographic, and echocardiographic variables using independent t-test and chi-square test. Results: The patients with RV systolic dysfunction were found to have higher Brain Natriuretic Peptide (BNP) values (P = 0.006) and worse functional status (New York Heart Association (NYHA) III-IV, P = 0.04) compared to group A. Besides, univariate analysis of the echocardiographic parameters revealed that the patients in group B had significantly (all P values < 0.05) higher Left Atrial Volume Index (LAVI), higher degree of left ventricular diastolic dysfunction (represented by LV-E/Em), higher degree of Functional Mitral Regurgitation (FMR), higher estimated Pulmonary Artery Systolic Pressure (PASP), and higher degree of RV diastolic dysfunction (represented by RV-E/ Em) Moreover, multivariate logistic regression analysis showed that severe FMR (P = 0.006) and RV-E/Em (P = 0.016) predicted RV systolic dysfunction independently. Conclusions: Advanced FMR and worse RV diastolic functions emerged as the independent predictors of RV systolic dysfunction in NICMP correlating to functional status and BNP levels.