Heart rate variability (HRV) represents one of the most promising quantitative markers of autonomic nervous system activity. It is commonly derived from RR interval of electrocardiographic (ECG) signal to evaluate the balance of sympathetic and parasympathetic responses due to the change in heart rhythm. However, in this present study, peak-to-peak interval variability of photoplethysmographic (PPG) signal has been used for the estimation of HRV. Further, to demonstrate the accuracy and feasibility of HRV extraction from PPG signal, finger-tip PPG and standard lead II ECG signals were simultaneously acquired under normal and deep breathing conditions. A comparative analysis of time- and frequency-domain measures of HRV was carried out. The correlation analysis of tachograms of ECG and PPG (Pearson linear correlation coefficient 0.9698 and 0.7389 under normal and deep respiration respectively) and error analysis of HRV parameters suggest that PPG can be considered as a simpler and reliable alternative for the HRV analysis and estimation of autonomic regulation.