Previous studies have identified the thrombus in portal vessels of the liver from autopsy, not biopsy, of patients with idiopathic portal hypertension (IPH). Present study shows a case of IPH in which portal thrombus was observed by image findings of ultrasonography (US) or magnetic resonant image (MRI). The patient was a female aged 65 who showed pancytopenia, spienomegaly, and esophageal varices. She was diagnosed as IPH based on the criterion of Ministry of Health and Welfare Reserch Comittee on IPH. We detected the mass lesion which was considered to be the thrombus in portal vessel by US and MRI.