Heart rate variability (HRV) corresponds to variations in heart rate or beat-beat time interval. This parameter reflects the status of the autonomic mechanisms of cardiovascular control, which may be influenced by changes characteristic of the life cycle of people, sedentary lifestyle, and various disease processes that directly or indirectly generate changes in the HRV and shift the autonomic balance, either towards greater sympathetic or parasympathetic influence on the heart. These antecedents support the use of HRV indices for the diagnosis and monitoring of various nosological entities in adults. However, there has been limited progress in the study of temporal variations in heart rhythm in the pediatric population. This article aims to describe the physiological and technical aspects of HRV in the pediatric population to provide a background that allows optimizing the application of these parameters in this age group.