Background Cardiac non-Hodgkin's lymphoma is rare and has a poor prognosis. Here we report a rare case mimicking pulmonary embolism. Case Description A 38-year-old woman suffered from severe dyspnea after cesarean section. With the clinical picture of fulminant central pulmonary embolism, lysis therapy was initiated. Further deterioration necessitated extracorporeal membrane oxygenation (ECMO) support and cardiosurgical intervention. Intraoperatively, a massive intravascular tumor obstructed the pulmonary bifurcation and was found to be B-cell lymphoma. Aggressive excision and pulmonary tree reconstruction improved the critical condition and initiated convalescence. Conclusion High suspicion in central pulmonary embolism and early cardiosurgical therapy after ineffective lysis are essential.