Background: Brachial plexus injury subsequent to an interscalene block (ISB) can be a difficult situation. Ultrasound-guided interscalene block (US-ISB) is currently the preferred technique; however, there is conflicting evidence in the existing literature about the elimination of this uncommon complication. Less is known about the nature and severity of the resulting neurological sequel as only few case studies are available in literature. Case description: A 28-year-old male underwent an elective removal of the dynamic compression plate and screws in a united fracture of humerus for constant pain with day-to-day activities. An ISB was performed under ultrasound guidance without any remarkable events during the procedure. Untowardly, the patient had experienced complete motor and sensory inactivity around shoulder and elbow in the postoperative period that persisted even at 3 weeks. Magnetic resonance imaging showed evidences of brachial plexus injury involving C5 and C6 roots extending to trunks. A conservative approach with rehabilitation and electrical muscle stimulation (EMS) was followed. Gradual recovery was observed and by 7 months he attained power to preinjury level. Conclusion: The practice of ISBs for upper limb surgeries does exhibit a rare risk of severe neuronal injury, even with established safe practices using ultrasound guidance. There are inconsistent evidences in the literature regarding permanent damage to brachial plexus following US-ISB and the resulting plexopathy shows complete recovery with conservative management. Clinical significance: Ultrasound guidance for ISBs may not be totally immune to neurological injury; however, the magnitude is of lesser severity and spontaneous recovery should be the rule.