Different internal jugular vein (IJV) abnormalities can be found in patients with multiple sclerosis (MS): stenoses, complete occlusion, distortions and intraluminal structures, such as membranes, webs and inverted valves. IJV duplication is a very rare phenomenon. We report a case of right IJV duplication as an incidental finding during IJV morphological and haemodynamic assessment in a patient with MS. A 55-year-old female patient was admitted to our Institute for IJV and vertebral veins morphological and haemodynamic assessment. During the last seven years she had been treated for MS. Colour Doppler ultrasonography in our patient did not reveal IJV or vertebral veins stenoses or abnormal valves, but instead right IJV duplication. This finding was confirmed using multislice computed tomography angiography and by selective phlebography. In conclusion, to our knowledge, a case of IJV duplication in a patient with MS has not been described yet. This further venous malformation can be assessed by the means of Doppler ultrasounds.