Background: Heart rate variability (HRV) depicts the functional status of the autonomic nervous system and its effects on sinus node. Objective: The aim of the study was to analyze heart rate variability (HRV) parameters in patients with heart failure with reduced ejection fraction (HFrEF) and to assess correlation between HRV parameters and functional capacity of the study group (assessed by NYHA class and 6 MWT). Subjects and Methods: This study included a total of 80 patients with chronic heart failure with reduced ejection fraction, attending at the Outpatient Clinic, Department of Cardiology, Al-Azhar (Al-Hussein) University Hospital. This study was conducted between December 2018 to October 2019. Patients were divided into four groups according to New York Heart association functional classification (NYHA). All patients were subjected to cardiac tests mainly ECGs, Echocardiography and 24 hours Holter monitoring. Results: High statistically significant difference was found between the four groups regarding HRV parameters (SDNN rMSSD, pNN50 and LF/HF ratio) and 6MWT duration. There was positive correlation between premature ventricular contractions (PVCs) burden and ANS indices (LF/HF). Conclusion: Disturbed cardiac autonomic function was found in patients with heart failure with reduced ejection fraction (HFrEF). HRV parameters have strong positive correlation with NYHA functional class and with 6MWT distance in patients with HF. Impaired autonomic function was associated with higher PVCs burden even in patients with same NYHA class.