Background: Common peroneal mononeuropathy at the fibular neck (CPN) is one of the most frequent neuropathies of the lower extremities. Nerve conduction studies (NCS) have been used to confirm the diagnosis of CPN and localize common peroneal nerve abnormalities. High-resolution ultrasonography (HRUS) can aid in assessing the size of the common peroneal nerve. Aim: Was to evaluate the superficial peroneal sensory potential (SPSP) and HRUS role in the confirmation of CPN. Methods: This study was conducted on 70 patients presented with clinical and motor electrophysiological evidence of common peroneal neuropathy at the fibular neck and 70 controls. Clinical assessment, electrophysiological evaluations, and HRUS at the fibular neck were done. Results: All the patients were electrophysiologically proven to have common peroneal motor neuropathy at the fibular neck, and seven of them showed abnormalities in nerve conduction studies only. The patients showed smaller common peroneal nerve motor and sensory responses and much larger cross-sectional area (CSA) of the common peroneal nerve at the fibular neck when compared with the controls. NCS and EMG positive findings are the most significant factor related to the increased HRUS CSA. Affected SPSP is significantly detected in patients with axonal affection. CSA of common peroneal nerve at the fibular neck showed a significant positive correlation with body mass index, motor, and sensory latencies. Also, it showed a significant negative correlation with motor and sensory amplitudes. HRUS CSA localized the lesion at the fibular neck with sensitivity and specificity 83% and 53% respectively. CSA plus SPSP affection sensitivity and specificity in confirming CPN were 91.9% and 89%. Conclusion: HRUS CSA plus affected SPSP improve the diagnosis of CPN compared to standard electrophysiological criteria. Recommendation: Further studies on a wider scale for detection of their role in the prediction of prognosis in CPN.