We aimed to investigate the predictive value of left atrium (LA) and left ventricle (LV) longitudinal strain derived by CMR-FT early after ST-segment elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (pPCI). Patients with STEMI who received pPCI and completed CMR within the following week were enrolled. LA and LV longitudinal strain parameters were derived from cine CMR by FT; conventional CMR indexes were also performed. The primary endpoint was the occurrence of major cardiovascular adverse events (MACE), defined as a composite of death, reinfarction, and congestive heart failure (HF). 276 participants (median age, 57 years, IQR, 48-66 years; 85% men) were included in this study. CMR was usually completed on the 5 (IQR,4-7) days after pPCI. During a median follow-up of 16 months, MACE occurred in 35 (12.7%) participants. Multivariable Cox regression analysis showed that LA conduit strain (HR 0.91, 95%CI: 0.84, 0.98, p = 0.013) and LV global longitudinal strain (HR 1.17, 95%CI: 1.03, 1.34, p = 0.016) remained independently associated with MACE. Participants with impaired LA conduit strain (≤ 12.8%) and LV global longitudinal strain (> -13.1%) had a higher risk of MACE than those with preserved. Longitudinal strain of LA and LV could provide independent prognostic information in STEMI patients, and comprehensive assessment of Left atrial and ventricular longitudinal strain significantly improved the prognosis.