A 61-year-old female patient with advanced liver cancer, with a medical history of more than one year, had received various chemotherapy and targeted drugs in the past. Due to disease progression and adverse reactions, the treatment regimen was adjusted to atezolizumab monotherapy. After using atezolizumab for 16 cycles, the patient developed hematemesis with a hemoglobin level of 44 g·L^–1. Gastrointestinal endoscopy revealed extensive erosion of the stomach and duodenum, and the patient was diagnosed with upper gastrointestinal bleeding. Considering the correlation with atezolizumab, a causality assessment using the Naranjo Assessment Scale was "likely". After drug discontinuation and symptomatic support treatment, the patient’s hemoglobin level recovered to 61 g·L^–1. The patient was followed up at 8 weeks after discharge, and no digestive tract discomfort such as hematemesis and black stool occurred again. Atezolizumab has been on the market for a short time in China, and there is no related report of upper gastrointestinal bleeding with this drug in China. This case suggests that severe gastrointestinal adverse reactions of atezolizumab should be paid attention to in clinical treatment to ensure safe and effective medication for patients.

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