Testicular cancer is the most common solid organ malignancy among young males, with a good survival rate if detected in a timely manner. We describe a case where a previously well young adult male died suddenly due to previously undiagnosed metastatic testicular cancer with retroperitoneal lymphadenopathy, resulting in compression and invasion of the inferior vena cava and development of pulmonary thromboembolism. This was attributed to both mechanical compression of the inferior vena cava and the prothrombotic effect of cancer. This is an unusual presentation of seminoma, where diagnosis was only made upon discovery of the pulmonary thromboembolism at autopsy.