Abstract Aims In patients with ST-segment elevation myocardial infarction (STEMI), predicting left ventricular (LV) remodelling (LVR) and prognosis is important. We explored the clinical usefulness of three-dimensional (3D) speckle-tracking echocardiography to predict LVR and prognosis in STEMI. Methods and results The study group comprised 255 first STEMI patients (65 years; 210 men) treated with primary percutaneous coronary intervention between April 2008 and May 2012 at Yokohama City University Medical Center. Baseline global longitudinal strain (GLS) was measured with two-dimensional (2D) and 3D speckle-tracking echocardiography. Within 48 of admission, standard 2D echocardiography and 3D full-volume imaging were performed, and 2D-GLS and 3D-GLS were calculated. Infarct size was estimated by 99mTc-sestamibi single-photon emission computed tomography. Echocardiography was performed at 1 year repeatedly in 239 patients. The primary endpoint was LVR, defined as an increase of 20% of LV end-diastolic volume index and major adverse cardiac and cerebrovascular events (MACE: cardiac death, non-fatal MI, heart failure, and ischaemic stroke) at 1 year, and the secondary endpoint was cardiac death and heart failure. Patients were followed for 1 year; 64, 25, and 16 patients experienced LVR, MACE, and the secondary endpoint, respectively. Multivariate analysis revealed that 3D-GLS was the strongest predictor of LVR (odds ratio = 1.437, 95% CI: 1.047–2.257, P = 0.02), MACE (odds ratio = 1.443, 95% CI: 1.240–1.743, P = 0.0002), and the secondary end point (odds ratio = 1.596, 95% CI: 1.17–1.56, P < 0.0001). Receiver-operating characteristic curve analysis showed that 3D-GLS was superior to 2D-GLS in predicting LVR and 1-year prognosis. Conclusion 3D-GLS obtained immediately after STEMI is independently associated with LVR and 1-year prognosis.