AbstractTraumatic venous pseudoaneurysm is extremely rare. Only two cases of great saphenous venous (GSV) pseudoaneurysm have been reported. We present a case in which a gradually enlarged mass occurred at the calf after local injury. It was nonpulsatile and varied in size with posture. It was initially misdiagnosed by contrast MRI. Duplex ultrasound and surgical intervention eventually identified it as a GSV pseudoaneurysm. This case demonstrates the need for physicians to consider venous pseudoaneurysm as a possible diagnosis for nonpulsatile masses in patient with traumatic history, and to use Duplex ultrasound for adequate evaluation.