Drains are routinely used after thyroidectomy and lateral neck dissection. In rare cases, the drainage tube is broken and retained in the neck. It is difficult to identify the sonographic features of the remnant tube due to variable reasons. However, through comparative and phantom observations, we noticed the double-tract sign of the tube wall and drainage holes as the key points to solving this problem. We report such a case of the ultrasound-guided localization of a broken drainage tube that was retained in the patient.