Background: Anatomical, structural as well as severity of brachial plexus injuries is evaluated by magnetic resonance imaging which determines the type of treatment as well as the prognosis. However, limitations such as static imaging, availability, cost-effectiveness & complexity of procedure has led to search of cheaper diagnostic modalities like ultrasonography which has potency to overcome such limitations. Therefore, this study was carried out to assess efficacy of ultrasound in post ganglionic brachial plexus injury. Materials and Methods:A cross sectional comparative study was conducted in the department of Radio-diagnosis of Mahatma Gandhi Medical College and Research Institute from January 2021 to June 2022 amongst 23 patients diagnosed with traumatic & clinically consistent brachial plexus injury who underwent surgical intervention. The outcome measures assessed were level of injury, site of injury, neuroma, rupture, neuropraxia / nerve thickening / probable scar block. Results: The majority of the subjects were males, with left sided injuries accounting for 52.2%. Root injuries (47.8%) were more common than trunk, division (26% each). USG showed 81.8% sensitivity & 100% specificity for rupture; 100% sensitivity & 92.3% specificity for neuroma & 50% sensitivity for nerve thickening. We recorded sensitivity & specificity rate of 100% for rupture, neuroma & nerve thickening on assessment by MRI. USG could not pick up T1 root injuries and lower trunk injuries. Conclusion: Ultrasonography recorded a high degree of accuracy in identifying the postganglionic brachial plexus injury associated with proximal roots, divisions, upper and middle trunks in the lateral region of the neck while the imaging in lower trunk was limited. Therefore, we conclude that ultrasonography supersedes limitations of MRI such as static imaging, expensive & technique sensitivity, which makes it a more lucrative diagnostic modality for studying the brachial plexus in adjunct or absence of MRI.