To our knowledge, this first reported STEMI after pegfilgrastim warrants vigilance for leukocytosis-related thromboembolic complications in oncology patients.<h4>Take-home-messages</h4>G-CSF-induced leukocytosis should be considered as a rare cause of acute myocardial infarction in patients without significant cardiovascular history. Here, CSF3 is linked to Increased total leukocyte count.