This review discusses the immune mechanisms and clinical manifestations of immune-related adverse events (irAEs) caused by immune checkpoint inhibitors (ICIs) used in cancer immunotherapy. ICIs, such as anti-CTLA4 and anti-PD1/PD-L1, work by blocking inhibitory signals in the immune system to enhance anti-tumor responses. However, they can also disrupt self-tolerance, leading to irAEs that affect various organs, including the skin, gastrointestinal tract, endocrine system, and lungs. The review highlights that irAEs are more common with PD1/PD-L1 inhibitors, while CTLA4 inhibitors are more frequently associated with neurological, cardiovascular, and hematological toxicities. The mechanisms underlying irAEs include the activation of autoreactive T and B cells, the release of self-antigens, and the production of autoantibodies. The review also discusses the role of the gut microbiome, genetic background, and environmental factors in the development of irAEs. It emphasizes the need for further research to develop biomarkers for predicting immune toxicities and to improve the management of irAEs in clinical practice. The review concludes that understanding the pathophysiology of irAEs is crucial for optimizing the use of ICIs and minimizing their toxicities.This review discusses the immune mechanisms and clinical manifestations of immune-related adverse events (irAEs) caused by immune checkpoint inhibitors (ICIs) used in cancer immunotherapy. ICIs, such as anti-CTLA4 and anti-PD1/PD-L1, work by blocking inhibitory signals in the immune system to enhance anti-tumor responses. However, they can also disrupt self-tolerance, leading to irAEs that affect various organs, including the skin, gastrointestinal tract, endocrine system, and lungs. The review highlights that irAEs are more common with PD1/PD-L1 inhibitors, while CTLA4 inhibitors are more frequently associated with neurological, cardiovascular, and hematological toxicities. The mechanisms underlying irAEs include the activation of autoreactive T and B cells, the release of self-antigens, and the production of autoantibodies. The review also discusses the role of the gut microbiome, genetic background, and environmental factors in the development of irAEs. It emphasizes the need for further research to develop biomarkers for predicting immune toxicities and to improve the management of irAEs in clinical practice. The review concludes that understanding the pathophysiology of irAEs is crucial for optimizing the use of ICIs and minimizing their toxicities.