Introduction. Fibroma is considered as benign solitary tumor, which is the second most common among primary heart tumors in children. It rarely starts to regresses, contributes to the formation of hemodynamic disorders and congestive heart failure, as well as life-threatening arrhythmias, and also can lead to the development of sudden death. Aim. Informing physicians about a rare cardiac fibroma in children on the example of a clinical case. Material and methods. Describing a clinical case of patient K., 7 months old, who was referred to the cardiac surgery department for a planned operation to remove a left ventricular mass, which was diagnosed prenatally at 32 weeks. Results and discussion. A dynamic observation was carried out, during which, according to echocardiography and magnetic resonance imaging, an increase in the tumor from 35x25 mm to 70x35 mm and the formation of mitral stenosis were noted. The average pressure gradient in the mitral valve increased from 2 to 11 mm Hg there was a limitation of the mobility of its valves. A partial resection of the tumor was performed. Morphological and immunohistochemical studies confirmed the diagnosis of fibroma. The postoperative period proceeded well. Conclusion. Cardiac fibromas in children, regardless to the clinical course of the disease, require long-term monitoring of patients with an electrocardiological study, echocardiography and magnetic resonance imaging method, and if there is a threat of complications, surgical removal of the tumor.