Background: Hereditary transthyretin amyloid cardiomyopathy (ATTR-CM) is a progressive and fatal disease. A97S (p.Ala117Ser) is the most common transthyretin geneticmutation in Taiwan. Tafamidis is a transthyretin stabilizer, and it has been shown to improve outcomes. However, its effect on A97S ATTR-CM subtypes remains unknown. Objectives: This study aimed to investigate the efficacy of tafamidis in patients with hereditary A97S ATTR-CM after 6 months of treatment. Methods:We retrospectively analyzed ATTR-CM patients who received tafamidis (61 mg/day) treatment at National Taiwan University Hospital. Functional status, biochemistry and echocardiography were measured at baseline and after 6 months of tafamidis treatment. The outcomemeasure was to compare the N-terminal pro-brain natriuretic peptide (NT-proBNP) level at baseline and after 6 months of tafamidis treatment. Results: Twenty patients were enrolled in this study. Their mean age was 63.0 5.8 years and 75% were men. The baseline left ventricular (LV) mass index was 200.9 63.9 g/m2, and the baseline LV ejection fraction was 58.9 13.5%. After 6 months of treatment, the log NT-proBNP level significantly improved from 2.9 0.6 to 2.7 0.5 (p = 0.036). Subgroup analysis showed that the LV posterior wall thickness and left atrial diameter were significantly higher in the patients with improved NT-proBNP, suggesting the benefits of tafamidis for ATTR-CM patients with severe cardiac involvement. Conclusions: The patients with hereditary A97S ATTR-CM in this study had decreased levels of NT-proBNP after 6 months of tafamidis treatment, and this reduction was especially pronounced in those with more severe cardiac involvement.