A woman in her 60s presented to her family doctor with left lower extremity edema. She was referred to our hospital where a computed tomography scan revealed a mass lesion which compressing with the left common femoral vein . Ultrasonography did not reveal any thrombus; however, a mass lesion (23 × 13 × 6 mm) was identified near the left common femoral vein. The mass lesion did not deform on compression with the ultrasound probe and showed low or isoechoic ultrasonic characteristics with partition walls inside. The magnetic resonance imaging revealed a multifocal cystic structure, which was suggestive of a benign tumor, such as lymphangioma or adventitial cystic disease. The patient was diagnosed with femoral venous stenosis due to compression induced by adventitial cystic disease. The mass lesion was surgically resected, and the histological examination revealed multifocal cysts, which is consistent with adventitial cystic disease. Venous adventitial cystic disease is rare, accounting for only 5% of all cases. Herein, we report a rare case of venous adventitial cystic disease that was detected via ultrasonography