Lung ultrasound (LUS) has emerged as a useful tool in the acute phase of patients admitted for ST-segment-elevation myocardial infarction. However, its long-term significance remains uncertain, and risk scores do not include LUS findings as a predictor. This study aims to assess the 1-year prognostic value of LUS and its ability to enhance existing risk scores. This is a multicenter prospective cohort study involving 373 patients with ST-segment-elevation myocardial infarction. LUS was performed during the first 24 hours after angiography. LUS results were assessed both as a categorical (wet/dry lung) and continuous variable (LUS score). The primary end point comprised the following major adverse cardiovascular events: all-cause mortality or hospitalization for heart failure, acute coronary syndrome, or stroke within 1 year. We also evaluated whether LUS could enhance the predictive value of the GRACE (Global Registry of Acute Coronary Events) score. Major adverse cardiovascular events occurred in 51 (13.7%) patients over a median follow-up of 368 days. After multivariate analysis, the LUS score was an independent predictor (hazard ratio [HR], 1.06 [95% CI, 1.01-1.10]; P=0.009] for each additional B-line), whereas the categorical classification was an independent predictor in patients with ST-segment-elevation myocardial infarction Killip I (HR, 3.12 [95% CI, 1.34-7.31]; P=0.009). Incorporating LUS into GRACE resulted in a net reclassification index of 31.6% and a significant increase in the area under the curve; GRACE alone scored 0.705 compared with GRACE+LUS 0.791 (P=0.002). Detecting B-lines on LUS at the acute phase predicts major adverse cardiovascular events at 1 year in patients with ST-segment-elevation myocardial infarction and enhances the predictive value of the GRACE score. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT04526535.