We report the case of a 78-year-old patient with acute ST-elevation myocardial infarction treated with primary percutaneous coronary intervention (PCI) of the right coronary artery, subsequently found to have a large subepicardial mass. The patient underwent a non-invasive multimodal diagnostic work-up including cardiac computed tomography and cardiac magnetic resonance imaging, which led to the diagnosis of subepicardial hematoma following coronary perforation during primary PCI. Due to clinical stability and absence of active bleeding sources, the patient was managed conservatively with gradual absorption of the mass and favorable prognostic outcome.