Nerve injury in children is important to recognize early given the greater chance for recovery. Both children and adults have better outcomes the sooner nerve injuries are recognized and repaired. Children have even better functional results after surgical repair, thought to be related to their neural plasticity. Ultrasound is a powerful diagnostic tool for grading and mapping peripheral nerve injury and is complementary to electromyography and nerve conduction studies. Nerve injuries can be classified into low and high grade with ultrasound adding essential prognostic information and aiding in patient management. High-grade nerve injuries likely require surgical intervention. This article will review nerve anatomy and injury grading systems that radiologists can learn quickly in order to accurately communicate with their clinical partners. A practical approach to describe the sonographic appearance of nerve injury will be discussed. This article will show radiologists how the added value of ultrasound for peripheral nerve injury can directly affect clinical management.