Introduction: Neuromuscular ultrasound has been increasingly used in the detection and diagnosis of amyotrophic lateral sclerosis (ALS), commonly characterized by peripheral nerve atrophy, degeneration, and muscle fasciculations. The aim of this study was to assess the ultrasound characteristics of ALS patients. Methods: A total of 67 consecutive patients with sporadic ALS and 19 with ALS mimics (63.16% peripheral neuropathy) were recruited. Ultrasound and electrophysiological examinations were performed; the peripheral nerve cross-sectional area (CSA) and fasciculation grades were compared between the groups, and correlations between ultrasound and electrophysiological data in ALS patients were determined. Results: ALS patients had smaller proximal median and ulnar nerve CSAs than those of ALS mimics, who exhibited asymmetric changes. Fasciculation differences in the trapezius, triceps brachii, extensor digitorum communis, thenar, and first dorsal interosseous muscles were observed. In ALS patients, the CSA and fasciculation relative scores were correlated with electrophysiological indicators. Conclusion: Ultrasound is a valuable tool for monitoring peripheral nerve CSA and muscle fasciculations, both of which correlate with electrophysiological indices, in ALS patients.