Immune checkpoint inhibitors are drugs used with increasing frequency in anticancer therapy. Cardiovascular complications are rare after their use, but they can be fatal. They can manifest as arrhythmias, myocarditis, pericarditis, left ventricular failure, takotsubo cardiomyopathy, or acute coronary syndrome. Depending on the clinical form of cardiotoxicity, various methods are used for diagnosis, including determination of cardiac and non-cardiac biomarkers, and the presence of characteristic changes on electrocardiography, transthoracic echocardiography, or cardiac magnetic resonance imaging (MRI). Surveillance involves capturing patients at risk and performing routine tests, which include a general cardiovascular evaluation, ECG, transthoracic echocardiography, and determination of cardiac troponins and natriuretic peptides. Recent publications point to the potential value of markers such as high-sensitivity troponins, microRNA, C-reactive protein, neutrophil-to-lymphocyte ratio, neutrophil-to-eosinophilia ratio, global longitudinal strain, and myocardial strain visible on echocardiography and cardiac MRI. The goal is to accelerate the detection of cardiac complications after immune checkpoint inhibitors and reduce mortality.