Abstract: A 52-year-old female patient was diagnosed with eosinophilic granulomatosis with polyangiitis (EGPA), asthma and allergic rhinitis and was treated with mepolizumab (100 mg, once every 4 weeks). Three days after the second administration, the patient developed dark yellow urine, and abnormal liver function indicators were found on day 6 after administration. Laboratory tests showed total bilirubin (TBIL) of 22 μmol/L, direct bilirubin (DBIL) of 14.9 μmol/L, alanine aminotransferase (ALT) of 461 U/L, aspartate aminotransferase (AST) of 129 U/L, and alkaline phosphatase (ALP) of 296 U/L. After comprehensive assessment, it was considered that mepolizumab caused drug-induced liver injury in the patient. Magnesium isoglycyrrhizinate, glutathione, and ursodeoxycholic acid were used for liver protection. Five days later, the urine color became lighter and liver function indicators improved (TBIL 17.4 μmol/L, DBIL 9.8 μmol/L, ALT 214 U/L, AST 85 U/L, ALP 226 U/L). After about 2 weeks of continued liver protection treatment, liver function returned to normal. Mepolizumab treatment was suspended and during the follow-up for about half one year, the patient did not experience liver function abnormalities or other discomforts again.