Abstract: Immune checkpoint inhibitors (ICIs) have greatly improved clinical outcomes in multiple cancer types and are regarded as a new beginning of cancer immunotherapy. However, high-grade immune-related adverse events can occur. Cardiotoxic effects are not common, but are often serious complications with a relatively high mortality. Patients may have symptoms of fatigue, shortness of breath, chest pain, and palpitation. The laboratory indexes showed the increase of troponin and N-terminal B-type natriuretic peptide (NT-proBNP). The electrocardiogram shows that there may be a new conduction block. Cardiac magnetic resonance (CMR) shows myocarditis, and about half of the patients show left ventricular ejection fraction less than 50% by echocardiography. Endocardial biopsy is the gold standard for diagnosis, and the common histological manifestation is lymphocyte infiltration dominated by T cells. Early use of sufficient steroids is the main treatment, and immune-suppressants such as infliximab and immunoglobulin can be used as appropriate.For all patients using ICIs, especially those with a history of diabetes, autoimmune disease or combined treatment, it is recommended to closely monitor the symptoms such as palpitation, shortness of breath, fatigue and troponin, NT-proBNP and other indexes in the early stage of treatment.