We aimed to correlate functional disability, electrophysiology, and nerve ultrasound in patients after Guillain-Barré syndrome (GBS). Seventy-five healthy controls and 41 post-GBS patients (mean 3.4 years, SD ± 2.91 years after onset) underwent clinical, sonographic, and electrophysiological evaluation. Compared to healthy controls, the post-GBS patients showed: (1) a mean Rasch-built Overall Disability Scale score of 31.8 (SD ± 11.6), modified Rasch-built fatigue severity scale score of 15.6 (SD ± 3.2), Medical Research Council sum score of 22 (SD ± 5.6); (2) electrophysiological signs of permanent axonal loss in the majority of the peripheral nerves; (3) sonographical evidence of higher cross-sectional area values (CSA) of the ulnar (elbow, p < 0.001), radial (spiral groove, p < 0.001), tibial nerve (popliteal fossa, p < 0.001) and brachial plexus (supraclavicular space, p < 0.001). No correlation between sonographic and electrophysiological findings was found. Neither nerve ultrasound nor electrophysiology correlated with muscle strength, overall disability, and fatigue scale. Compared to healthy controls, post-GBS patients had significant functional disability. Despite significant abnormalities in both electrophysiology and ultrasound compared to healthy controls, neither electrophysiology nor nerve ultrasound correlated with functional disability of these patients.