Background: Dapagliflozin and sodium–glucose cotransporter 2 inhibitors reduce the risk of cardiac death and hospitalization for heart failure (HF), regardless of the patient’s status with type 2 diabetes mellitus (T2D). Further investigation is required to ascertain the impact of these drugs on patients suffering from acute myocardial infarction (AMI) complicated by acute decompensated heart failure (ADHF). Methods: In retrospective research comprising 371 patients with AMI complicated by ADHF of Killip class II–IV and left ventricular ejection fraction ≤40%, the effectiveness of dapagliflozin at a dosage of 10 mg once a day was compared to standard of care alone. The main results consisted of a primary composite outcome, which encompassed either cardiovascular (CV) mortality or hospitalization due to HF. Additional clinical outcomes assessed were CV mortality, hospitalization due to HF, and changes in laboratory measurements, including glycosylated hemoglobin, N-terminal prohormone B-type natriuretic peptide, and estimated glomerular filtration rate (eGFR). Results: In the group that received dapagliflozin, 10.7% of patients experienced a primary composite outcome event, while in the group that did not receive dapagliflozin, 24.9% of patients experienced one. The median follow-up period was 12.4 months, and the hazard ratio for CV death or hospitalization for HF was 0.67 (95% confidence interval [CI], 0.65–0.86; P < 0.001). Hazard ratio, 0.68; 95% CI, 0.55–0.69; P < 0.001), the group given dapagliflozin had fewer HF hospitalizations overall than the group given a placebo. Dapagliflozin decreased the likelihood of serious kidney outcomes and decelerated the yearly decline in the eGFR (2.1% vs. 7.6%; P < 0.001). Conclusions: Patients with AMI complicated by ADHF who received dapagliflozin had a lower risk of CV death or HF hospitalization, regardless of their T2D status.