The combination of atezolizumab (ATZ) and bevacizumab (BVZ) was approved as first-line systemic therapy for advanced hepatocellular carcinoma (HCC) owing to its superior rates of response and patient survival. However, ATZ + BVZ is associated with increased risk of upper gastrointestinal (GI) bleeding, including arterial bleeding, which is rare and potentially fatal. We present a case of massive upper GI bleeding from a gastric pseudoaneurysm in a patient with advanced HCC who had been treated with ATZ + BVZ.A 67-year-old man presented with severe upper GI bleeding after atezolizumab (ATZ) + bevacizumab (BVZ) therapy for HCC. Endoscopy failed to detect the bleeding site. Digital subtraction angiography revealed a gastric artery pseudoaneurysm and contrast extravasation from the inferior splenic artery and a branch of the left gastric artery. Successful hemostasis was achieved with embolization.HCC patients who have been treated with ATZ + BVZ should be followed for 3 to 6 mo to monitor for development of massive GI bleeding. Diagnosis may require angiography. Embolization is an effective treatment.©The Author(s) 2023. Published by Baishideng Publishing Group Inc. All rights reserved.