Iron deficiency (ID) is common in patients with acute myocardial infarction (AMI). It is unknown whether patients with AMI combined with ID will benefit from iron supplementation therapy. This study aimed to assess the relationship between iron therapy and mortality in AMI patients. Retrospective analysis was performed in subjects screened from the Medical Information Mart in Intensive Care-IV database. The data were obtained from ICU patients admitted to Beth Israel Deaconess Medical Center between 2008 and 2019. The patients were divided into two groups according to iron treatment exposure. Propensity score matching (PSM) was performed in the original cohort at a 1:1 ratio. Univariate and multivariate analyses were performed to adjust for confounding factors. The primary outcome was 28-day mortality. A total of 426 patients were included in this study. After 1:1 PSM, 208 patients were analyzed. Iron treatment was associated with a lower risk of 28-day mortality (9 deaths (8.65%) in the iron treatment group vs. 21 deaths (20.19%) in the non-iron treatment group; HR = 0.39; 95% CI = 0.17-0.89; p = 0.025) and in-hospital mortality (4 deaths (3.85%) in the iron treatment group vs. 12 deaths (11.54%) in the non-iron treatment group; OR, 0.15; 95% CI, 0.03-0.74; p = 0.029). Iron treatment was associated with reduced 28-day mortality in patients with AMI combined with ID. Iron treatment had no significant effect on the length of hospitalization or the length of ICU stay. Prospective studies are needed to verify this conclusion.