Background: Aortic stenosis (AS) and transthyretin amyloid cardiomyopathy (ATTR-CM) are common in the elderly. We evaluated the usefulness of two-dimensional (2D) speckle strain imaging to diagnose concomitant ATTR-CM in patients with AS. Methods and Results: We analyzed 72 consecutive patients with moderate to severe AS who underwent 99m Tc-pyrophosphate (PYP) scintigraphy, a useful modality for diagnosis of ATTR-CM, at Kumamoto University Hospital from January 2012 to September 2020. There were no significant differences in the baseline clinical characteristics or conventional echocardiographic findings between the 99m Tc-PYP scintigraphy-positive and -negative groups. In 2D speckle strain imaging of the left ventricle, the relative apical longitudinal strain (LS) index [apical LS/ (basal LS + mid LS)] was significantly higher in the 99m Tc-PYP scintigraphy-positive than -negative group (p<0.05). In 2D speckle strain imaging of the left atrium (LA), the peak longitudinal strain rate (LSR) and the late LSR were significantly lower in the 99m Tc-PYP scintigraphy-positive than -negative group (peak LSR:0.36±0.14 vs. 0.55±0.20, p<0.05 and late LSR:0.26±0.25 vs. 0.52±0.29, p<0.05, respectively). In the receiver-operating-characteristic analysis, the peak LSR in the LA was the most effective echocardiographic parameter for 99m Tc-PYP scintigraphy positivity (area-under-the-curve, 0.79). Multivariable logistic analysis using two forced inclusion models identified the peak LSR in the LA was more significant factor of 99m Tc-PYP scintigraphy positivity in patients with AS. Conclusion: The peak LSR in the LA may be a useful predictor of the presence of ATTR-CM in patients with AS.