The prognostic value of left atrial (LA) volume is well-established in acute myocardial infarction (AMI) patients. LA strain provides further patophysological insights. In the present study, we evaluated LA volume and LA strain in AMI patients including those with atrial fibrillation (AF). The aim of the study was to determine if LA strain provide additional prognostic value. Patients with AMI underwent two-dimensional echocardiography within 72 h of admission. The primary outcome was a composite of all-cause mortality and major adverse cardiovascular events. Cox regression analyses were performed. We included 501 patients and during follow-up, 132 patients (26.4%) met the primary outcome. Left ventricular (LV) global longitudinal strain (GLS) (HR 0.94 [95% CI 0.88–0.99], p = 0.029), indexed LA volume (LAVi) (HR 1.02 [95% CI 1.00–1.04], p = 0.015), and LA reservoir strain (HR 0.96 [95% CI 0.93–0.99], p = 0.017) were all independently associated with the primary outcome. A univariate Cox model conducted on the AF patients (n = 32) revealed that LA reservoir strain remained significantly associated with the primary outcome, while LV GLS and LAVi were not significant. The prognostic value of LA reservoir strain was comparable to LA volume and LV GLS, and might even be better in AF patients.