Wearable sensors have become integral tools for monitoring biomechanical and physiologic aspects of athletic training and performance. A prominent trend in fitness technology, wearable devices now measure a variety of health characteristics, including movement and posture, physiologic measures (eg, heart rate and energy expenditure), and fluid and electrolyte losses, to understand an athlete’s physiologic responses during activity. Sleep has proven integral to athletic performance, and sleep monitoring wearable devices (eg, watches, rings, and headbands) use various measures, such as actigraphy and pulse oximetry, to analyze sleep quality. Young athletes benefit from wearable devices during training sessions, where multimodal data are collected and analyzed to assess performance. Wearable devices are also useful for resistance training, biofeedback, and electrical muscle stimulation, providing athletes with tools to optimize their training regimens. Moreover, these devices play a crucial role in athlete safety by monitoring cardiac physiology, head impacts, and muscle rehabilitation after injury. We provide a comprehensive review of current wearable technology and its application in youth athletics, describe where and how these sensors are used to help enhance physiologic, biomechanical, and performance parameters, and discuss future directions for wearable devices to advance sports science and athlete management.