Tafamidis meglumine is a novel medicine that has been shown to slow the progression of peripheral neurological impairment in patients with hereditary transthyretin amyloidosis (ATTR). However, the efficacy of tafamidis against ATTR-related cardiac amyloidosis remains unclear. A 72-year-old woman had cardiac hypertrophy and axonopathy in her lower legs. Endomyocardial biopsy revealed an infiltrative cardiomyopathy consistent with amyloidosis. Immunostaining and genetic studies confirmed the diagnosis of ATTR, and tafamidis was started subsequently. Two years after the initiation of tafamidis treatment, electromyography demonstrated no change in the axonopathy in her lower legs; however, electrocardiography displayed QRS prolongation, and echocardiography disclosed an increase in interventricular septal thickness. Endomyocardial biopsy indicated that transthyretin amyloid infiltration of the myocardium was not reduced. In this case, there was no apparent progression of axonopathy, although there were signs of worsening amyloid cardiomyopathy during the treatment with tafamidis.