A 69-year-old woman presented with a 4-month history of dyspnoea and radiating upper-right quadrant pain and oedema in her lower extremities for more than 20 days. The ultrasonographic study of the heart revealed the adherence of a substantive hypoechoic mass (73 x 34 mm) to the antelateral wall of the pulmonary artery and resultant pulmonary stenosis. Computed tomographic imaging of the pulmonary artery revealed an irregularly shaped filling defect (approximately 41 x 39 x 59 mm) in the main pulmonary artery. The boundary of the defect was irregular, but demarcation with healthy tissue was clear. After surgical treatment, the histologic and immunohistochemical assays revealed a primary pulmonary artery rhabdomyosarcoma. Pulmonary artery rhabdomyosarcomas are usually misdiagnosed as other pulmonary artery obstructive diseases. There should be a greater focus of clinical attention and resection is the appropriate surgical treatment for such malignant tumours.