Left atrial (LA) dysfunction (LAD) and thrombi have been described in systemic light chain (AL) cardiac amyloidosis (CA). The causes and consequences of these alterations are unclear.To (1) demonstrate that LA 2D-strain echocardiography (2D-SE) is useful to analyze LAD; (2) explore causes, consequences and association of this dysfunction with thromboembolic events (TE) in the three major types of CA.Seventy-six patients with CA and in sinus-rhythm were included. 21 had AL, 42 hereditary transthyretin (m-TTR) and 13 wild-type (wt-TTR) CA. History of TE was recorded at baseline. Global and regional LA longitudinal strain (LS) were measured using 2D-SE. Peak atrial LS (PALS-4C) was negatively correlated to NT-proBNP (r=−0.6, P<0.0001) and to LA end-diastolic volume (r=−0.48, P<0.0001). LA volume was higher and PALS-4C more altered in wt-TTR compared to the other groups. The 19 patients with a history of TE had a significantly lower PALS-4C compared to those without (P=0.003). Multivariate analysis identified PALS-4C as the only LA echocardiographic independent factor of mortality with an optimal cutoff-value of 9.5% (AUC 0.75, 95% CI 0.60–0.89). When including all the variables, NT-proBNP became the only independent marker of prognosis.Atrial function estimated by 2D-SE is useful to identify patients at risk of death and might be helpful to select those that may benefit from preventive anticoagulant treatment.