This research aimed to assess the effect of a specific herbal agent to gain weight as the potential cause of Portal Vein Thrombosis (PVT) and hepatic damage. In this study, we reported a 24-year-old man who referred to the Tehran University of Medical Sciences (TUMS) hospital complaining of 4-day progressive abdominal pain. The patient’ s abdominal pain was generalized with a mild tenderness over the epigastric region. He complained of nausea, vomiting, and loss of appetite. However, he reported no hematemesis, melena, or dyspnea, with unremarkable past and family medical history. An abdominopelvic ultrasound and Computed Tomography (CT) scan were conducted for further investigation of the patient, which revealed extended filling defect in portal vein and its branches. In addition, the evidence of liver hypoperfusion was found because of geographic hypodense lesion seen in the major parts of the right lobe and the IV segment of the left lobe. The patient was further assessed for any acquired or inherited potential prothrombotic state associated with abdominal vein thrombosis, which were all rolled out. However, his round moon face, purplish striae, and the back acne increased the suspicion of drug side effects. Finally, a herbal agent (Fereshteh tablet) was found as the cause of the patient’ disease. He consumed the tablet to gain weight from 3 months ago. His thrombosis was treated with subcutaneous enoxaparin, as well as oral intake of warfarin. He was recommended to check liver function regularly at outpatient hepatobiliary clinic after discharge.