We herein report a 20-year-old woman who developed eosinophilic granulomatosis with polyangiitis (EGPA) and portal vein thrombosis (PVT). EGPA was diagnosed based on the patient's history of asthma, hypereosinophilia, and mononeuritis complex. Thrombocytopenia and liver dysfunction were observed, necessitating contrast-enhanced computed tomography (CECT), which revealed PVT. Her symptoms soon improved with glucocorticoids and anticoagulation therapy. As patients with EGPA often suffer from asthma, they can be hesitant to undergo CECT. However, if patients with EGPA show uncertain thrombocytopenia with liver dysfunction, a further evaluation using CECT is warranted to detect PVT.