Solitary fibrous tumors (SFTs) are rare neoplasms originating from fibroblastic mesenchymal cells. This case report details a 43-year-old female patient with cardiac SFT, a rarity in the medical literature, who presented with palpitations and a known malignancy. Supraventricular tachycardia was diagnosed in the emergency department, and a subsequent echocardiography revealed a giant mass in the left atrium after sinus rhythm restoration. The mass, causing symptomatic severe mitral stenosis, necessitated surgical intervention. Pathological examination of the surgical specimens confirmed the diagnosis of SFT. Cardiac masses are extremely rare in clinical practice, and the literature on SFTs is primarily limited to case reports. More research is needed due to the scarcity of information on managing this condition.