Most brachial plexus injuries are a result of high velocity, traction-type traumas. In severe cases, brachial plexus injury results in a variable functional loss of the upper extremities. Steroid has been reported to delaye degeneration and improve regeneration of the injured nerve. Here, steroid was injected into the brachial plexus compartment in a 5-year-old female with brachial plexus injury caused by a traffic accident. After the injection of steroid into the compartment of the injured brachial plexus, motor and sensory functions of the left upper extremity were much improved. Steroid injection should be considered as another option of conservative treatment in patients with brachial plexus injury before or after operation.