Identification of patients with reversible left ventricular (LV) dysfunction has important prognostic implications after acute myocardial infarction (AMI). This study aimed to determine the value of LV segmental and global longitudinal strains assessed with 3-dimensional (3D) speckle-tracking analysis in predicting improvement of LV function after AMI. One hundred fifty-three patients (80% men, 59 ± 11 years old) with AMI and treated with primary percutaneous coronary intervention underwent 3D echocardiography. LV segmental and global 3D longitudinal strains were assessed with speckle-tracking analysis using a novel dedicated software. At 6-month follow-up, improvement in segmental LV function was defined as a decrease of ≥1 grade in segmental wall motion score. Improvement in global LV function was defined as an absolute improvement ≥5% in LV ejection fraction. Segments with functional improvement at follow-up showed a significantly higher baseline 3D longitudinal strain compared to segments without improvement (-16.4 ± 4.0% vs -7.6 ± 3.5%, p <0.001). A cut-off value of -11.1% for segmental 3D longitudinal strain had 92% sensitivity and 91% specificity in predicting functional improvement. In addition, 67 patients (44%) showed an improvement in global LV function at 6-month follow-up. These patients showed significantly higher baseline global 3D longitudinal strain compared to patients without improvement (-16.7 ± 2.1% vs -13.3 ± 2.6%, p <0.001). Global 3D longitudinal strain provided incremental value over clinical and conventional echocardiographic variables in predicting global LV function improvement (c-statistic improved from 0.64 to 0.71 to 0.84). In conclusion, longitudinal strain assessed by 3D speckle-tracking analysis is an important predictor for segmental and global LV function improvement after AMI.