We describe an unusually located venous aneurysm found incidentally in a 46-year-old man that was presumptively diagnosed as a retroperitoneal mass near the left renal hilum. He presented for constipation and weight loss; an abdominal ultrasound scan disclosed an anechoic lesion in the left retroperitoneum. Abdominal CT showed a 3-cm mass with low density located at the junction of the left para-aortic and perirenal hilar regions that was initially suspected of being metastatic lymphadenopathy with an unknown primary origin or a neurogenic tumor. The mass was resected by a laparoscopic approach, which revealed a round mass with a smooth capsule and roots connecting to the paraspinal muscles. On pathologic examination, the mass showed classic features of a venous aneurysm. At 12-month follow-up, no local recurrence or malignancy was documented.