Objectives: To present a case of a leiomyosarcoma of the left atrium, presenting as exertional dyspnea in a middle-aged Filipino. This study likewise presents a review of current literature.Results: A 44 years old female presented with a three-day history of exertional dyspnea. Transesophageal echocardiography revealed a mass with pericardial effusion and a large mass occupying almost the entire left atrial cavity. She underwent complete excision with mitral valve repair. Histopathology revealed bundles of fascicles of spindle-shaped cells with eosinophilic infiltrates, positive for SMA, Caldesmon, and Vimentin, and a high Ki67 of >50% --consistent with primary leiomyosarcoma. No adjuvant chemotherapy was done. Within three months of post-operation and lost to follow-up, the patient noted the recurrence of dyspnea. Echocardiography revealed the recurrence of the mass, again obstructing the left atrium.Metastatic lesions were also on both lungs. The patient was planned a 2nd resection of the mass, followed by systemic chemotherapy, but died due to obstructive heart failure.Summary/conclusion: Primary cardiac leiomyosarcomas (PCLMS) are extremely rare tumors. Studies reveal female preponderance with mean age of 48 years. The tumors seem to originate from the cardiac chambers, without the involvement of the pericardium and great vessels. Increased tumor burden, metastatic disease, high proliferative index, and high-grade tumors usually translate to a worse prognosis. Complete surgical resection of the tumor is still the mainstay of treatment followed by doxorubicin, ifosfamide, or dacarbazine-based regimens.