Although thrombosis in the terminal part of thoracic duct has been described in patients with head and neck cancer and upper vein thrombosis, normally medical imaging is not successful in depicting such lymphatic thrombosis. This case series is about three patients with acute onset of cervical lymphedema following minor trauma or exceptional physical strain. Using high‐resolution ultrasound, it was possible to detect a thrombus formation in the terminal parts of the thoracic duct or the lymph duct. Within a few weeks all patients recovered without relapse for several years.