Subacute stent thrombosis is an uncommon but life-threatening complication of percutaneous coronary intervention (PCI). While mechanical and antiplatelet-related factors are most frequently implicated, systemic hypercoagulable conditions are increasingly recognized as important contributors. Acute myeloid leukemia (AML) is associated with complex hemostatic abnormalities that may predispose to both venous and arterial thrombosis, particularly in the presence of hyperleukocytosis. We report the case of a 33-year-old male with minimal cardiovascular risk factors who presented with ST-segment elevation myocardial infarction and was found to have a large thrombus burden in the proximal left anterior descending artery. Despite pharmacologic reperfusion and subsequent drug-eluting stent implantation, he re-presented ten days after discharge with subacute stent thrombosis and additional thrombotic involvement of multiple coronary vessels, leading to hemodynamic instability. Although he reported adherence to dual antiplatelet therapy, laboratory evaluation revealed rapidly progressive leukocytosis accompanied by anemia and thrombocytopenia. Further hematologic workup confirmed a diagnosis of acute myeloid leukemia with profound hyperleukocytosis. Cytoreductive therapy was initiated, but the course was complicated by tumor lysis syndrome and acute kidney injury, necessitating renal replacement therapy prior to transfer for definitive oncologic management. This case highlights AML-associated hypercoagulability and hyperleukocytosis as potential contributors to early and recurrent coronary thrombosis following PCI. Leukostasis, endothelial activation, and blast-mediated procoagulant activity likely acted synergistically with stent-related endothelial injury to promote thrombosis despite standard antiplatelet therapy. Early or recurrent stent thrombosis, particularly in younger patients or in the presence of unexplained hematologic abnormalities, should prompt evaluation for underlying malignancy. Recognition of AML in this context is critical, as it may influence revascularization strategy, antithrombotic management, and overall prognosis.