Immune checkpoint inhibitors(ICIs)have been used to treat various malignant tumors,and benefit cancer patients.Cadonilimab is the first PD-1/CTLA-4 tumor dual ICIs approved in June 2022,and there have been no reports of ICIs associated myocarditis caused by Cadonilimab.This article introduces one case of severe ICIs related myocarditis diagnosed after 3 cycles of using Cadonilimab,and his condition was improved significant-ly after glucocorticoids treatment.This case highlights the potential risk of ICIs related myocarditis induced by Cadonilimab,providing insights for the diagnosis and treatment of ICIs related myocarditis.