Malignant peripheral nerve sheath tumour (MPNST) is an aggressive and uncommon cancer developing in the peripheral nerve sheath. Primary cardiac MPNST is an extremely rare finding, with no specific imaging and clinical characteristics. Only a handful of cases have been reported in the literature; thus, little is still known about them. Cardiac computed tomography (CT) and cardiac magnetic resonance imaging (CMRI) are important means of assessing cardiac morphology and function. The preferred course of treatment for this pathology is by full surgical resection of the tumour, with negative (clear) margins, followed by adjuvant radiotherapy and chemotherapy. We present the case of a 42-year-old woman with no significant cardiovascular symptoms who was incidentally diagnosed during routine transthoracic echocardiography (TTE) with a cardiac mass located in the left ventricle.