Thrombosis is one of the most dangerous complications of COVID-19. Due to the urgency of the problem, a clinical case of thrombosis in the left ventricular cavity and the development of acute heart failure after SARS-CoV2 infection is presented. Patient I., 1965 year of birth, was on inpatient treatment in the Republican Cardiological Dispensary (Cheboksary) with a diagnosis: New coronavirus infection, severe course. Coronary heart disease: paroxysmal form of tachysystole atrial fibrillation. Postinfarction cardiosclerosis. Complications of major disease: COVID-associated pneumonitis, alveolitis. Acute heart failure. Complaints of fever up to 38.8 °C, asthma attacks in a horizontal position. Coagulation profile: D-dimer 1012.00 ng/ml, fibrinogen: 17.9 g/l. Echocardiogram: a dense structure along the posterior wall of left ventricle with increased echogenicity is visualized. The ejection fraction is 20.79%. Electrocardiogram: atrial fibrillation, tachysystole form. Despite the treatment, heart and respiratory failure developed, which resulted in fatal outcome. Thrombotic masses sized 1×2.3×4.7 cm were found in a sectional examination of left ventricle field. A histological examination revealed wave-like deformations and fragmentation of muscle fibers in the heart tissue. Edema, areas of dystelectasis and hyaline membranes along the alveoli contour were found in the lung tissue. Thus, the patient developed thrombosis of the left ventricle with acute heart failure after SARS-CoV-2 infection.