This is a case report of a 45-year-old patient admitted with the symptom of bilateral leg swelling. Ultrasonography revealed a hyperechoic mass in the right lobe of the liver, which invaded the right hepatic vein (RHV) and extended into the inferior vena cava (IVC) and right atrium (RA). Based on the high alpha-fetoprotein (AFP) level and the ultrasonography findings, the patient was diagnosed as having hepatocellular carcinoma (HCC) with a RHV, IVC, and RA tumor thrombus and secondary Budd-Chiari syndrome (BCS). HCC with a tumor thrombus extending into the IVC and RA has rarely been observed, and as a cause of secondary BCS, this type of HCC has been even more rarely reported. K E Y W O R D S hepatocellular carcinoma, inferior vena cava, right atrium, tumor thrombus S U PP O RTI N G I N FO R M ATI O N Additional supporting information may be found online in the Supporting Information section. Movie S1. Transthoracic echocardiography, apical 4-chamber view, revealed a thrombus (yellow arrow) in the RA. RA = right atrium; RV = right ventricle; LA = left atrium; LV = left ventricle; TT = tumor thrombus; IVC = inferior vena cava. Movie S2. Transthoracic echocardiography showed the TT in the RA coming from the IVC and the thrombus in the RHV and IVC (red arrow). RA = right atrium; RV = right ventricle; TT = tumor thrombus; IVC = inferior vena cava; RHV = right hepatic vein. Movie S3. Abdominal ultrasound showed the TT coming from the IVC (red arrow) and integrating with the liver mass (white arrow). LV = left ventricle; RV = right ventricle; TT = tumor thrombus; IVC = inferior vena cava. Movie S4. Transthoracic echocardiography showed that the tumor thrombus in the RHV, IVC (red arrow) and RA was continuous. RA = right atrium; RV = right ventricle; TT = tumor thrombus; IVC = inferior vena cava; RHV = right hepatic vein. How to cite this article: Chen M, Huang X, Yang Q. Hepatocellular carcinoma with inferior vena cava and right atrial tumor thrombus: A case report. Echocardiography.