Despite advances in the management of ST-elevation myocardial infarction (STEMI), when associated with heart failure (HF) its prognosis remains ominous. This study assessed the differences in admission and mortality of HF complicating STEMI at admission (HFad) in a middle-income country. Data from the National Registry of STEMI of Argentina (ARGEN-IAM-ST) from January 1, 2016, to September 30, 2020, were analyzed. HFad was defined by the identification of Killip/Kimball ≥2 at admission. About 3174 patients were analyzed (22.3% had HFad). Patients with HFad were older, more often women, hypertensive, and diabetic. Received less reperfusion (87.6% vs 92.6%, P < 0.001) and had increased in-hospital mortality (28.4% vs 3.0%, P < 0.001). In multivariate analysis HFad was an independent predictor of death (OR: 4.88 95%CI: 3.33-7.18, P < 0.001) and reperfusion adjusted to HFad was associated with lower mortality (OR: 0.57 95%CI: 0.34-0.95, P = 0.03). HFad in STEMI is associated with a worse clinical profile, receives fewer reperfusion strategies, and carries a higher risk of in-hospital mortality while reperfusion reduces mortality.