Background and purpose We evaluated muscle echointensity as a marker for secondary axonal damage in patients with chronic inflammatory demyelinating polyneuropathy (CIDP) using ultrasonography. Findings were correlated with clinical disability and muscular strength. Methods Eighty patients with CIDP (40 with typical and 40 with atypical CIDP) were examined clinically, including assessment of Medical Research Council (MRC) sum score and Inflammatory Neuropathy Cause and Treatment Overall Disability Sum Score (INCAT‐ODSS). Echointensity in eight proximal and distal muscles of the arms and legs was evaluated by muscle ultrasonography using the Heckmatt scale. Results Alterations of echointensity occurred most frequently in the distal leg muscles, with a median (range) Heckmatt score of 1.5 (1–4). There were no differences between typical and atypical CIDP patients with regard to Heckmatt score. Alterations of echointensity correlated to disability and muscle strength. The arm score of the INCAT‐ODSS correlated to Heckmatt score for the distal arm muscles (r = 0.23, p = 0.046) and the leg score of the INCAT‐ODSS correlated to Heckmatt scores for the proximal (r = 0.34, p = 0.002) and distal leg muscles (r = 0.33, p = 0.004). MRC sum score, as well as individual MRC scores for arm and leg muscles, correlated to Heckmatt scores of the corresponding muscle groups (r = −0.25, p = 0.02 for MRC sum score). Conclusion Increased muscle echointensity, reflecting fibrosis and fatty infiltration due to secondary axonal damage, correlated to muscular strength and disability in a large cohort of CIDP patients. Alterations of echointensity occur in both typical and atypical CIDP patients and are pronounced in the distal leg muscles.