Budd–Chiari syndrome (BCS) is considered as a rare disease characterized by thrombotic or non-thrombotic obstruction of the venous outflow from hepatic vein into the inferior vena cava (IVC). A 21-year-old boy was admitted in the hospital with a 4‐days history of abdominal pain and vomiting. Colour Doppler evaluation revealed suspicious extrinsic compression, low flow of the inferior vena cava (IVC), and abnormal narrowing of hepatic veins. The patient underwent CT venography, by which caudate lobe hypertrophy, early enhancement of the caudate lobe and central zone of the liver, inhomogeneous mottled liver, flip-flop pattern ensues, and the slit-like narrowing of the hepatic IVC without hepatic veins identification. Furthermore, hepatic venous outflow obstruction suggested the diagnostic features of BCS based on CT imaging findings. Besides, the allele-specific PCR showed Janus kinase 2 (JAK2) V617F mutation.