A 3-year-old girl presenting with fever, mucocutaneous inflammation, and acute gastrointestinal symptoms met criteria for the multisystem inflammatory syndrome in children associated with COVID-19 (MIS-C). Echocardiography showed severely decreased left ventricular (LV) function with an apical mass. After treatment with intravenous (IV) immunoglobulin, IV steroids, anakinra, milrinone, and systemic anticoagulation, her LV function rapidly improved and the mass became increasingly mobile. Given the risk of systemic embolization, the mass was excised through left ventriculotomy and pathology confirmed a thrombus.