Immune checkpoint inhibitors (ICI) represent a class of drugs that has dramatically improved survival outcomes of patients with several solid and haematological malignancies. Due to their mechanism of action, treatment-related adverse events (AEs) induced by ICI are mostly immune-related AEs, which can affect any organ, including the cardiovascular system. Immune-related cardiac AEs are rare, occurring in less than 1% of patients receiving ICI. However, they are associated with a high fatality rate compared to other AEs. Together with an increasing awareness among physicians, cardiotoxicity of ICI requires further investigation to better understand the pathophysiology of this rare but possibly fatal complication, and to improve its diagnosis and treatment. The present narrative review aimed to describe the incidence and the underlying mechanism of ICIs’ cardiotoxicity, providing key messages for clinical practice for oncologists and cardiologists on their clinical manifestations and management.