Immune checkpoint inhibitors (ICIs) have revolutionized oncologic treatment, offering a novel and effective approach to personalized cancer immunotherapy. By targeting immune tolerance pathways, ICIs enhance T-cell-mediated tumor cytotoxicity. Despite their therapeutic efficacy, ICIs are associated with immune-related adverse events (irAEs), including severe cardiovascular complications like myocarditis, pericarditis, and vasculitis. ICI-related myocarditis, although uncommon, carries a high mortality rate of up to 50%, particularly in patients receiving combination therapies. This review examines the mechanisms of ICIs, highlights the clinical presentation of cardiac irAEs, and underscores the utility of cardiac magnetic resonance imaging (CMR) in the diagnosis of ICI-associated myocarditis. Through case studies, we illustrate the diagnostic and therapeutic strategies for ICI-related cardiac complications, highlighting the importance of multidisciplinary collaboration in mitigating morbidity and mortality.