Cancer immunotherapy has resulted in improved outcomes for patients with various solid and haematological cancers. However, the other side of the mirror is that the multiple immuno-modulating mechanism of actions of immunotherapies can result in antigen-specific autoimmune damage of various organ systems, which can lead to potentially serious immune-related adverse events if not promptly recognised and treated. Adverse events affecting nearly every organ system have been reported in association with cancer immunotherapy, with different immunotherapies resulting in distinct autoimmune manifestations related to their specific mode of action. Increasing use of immunotherapies has resulted in improved knowledge of safety profiles with the most frequent toxicities now well known. However, other less common adverse effects can also occur and are less well documented. All of these toxicities have variable times of onset and require careful monitoring, follow-up and management. They are usually reversible with appropriate and timely intervention but can become severe and even life-threatening if not recognised early enough. Specific management algorithms have been developed which aid early diagnosis and treatment and help to minimise life-threatening complications. Patient education for the early recognition of symptoms is also important. Increased understanding of the mechanisms and factors that influence risk of immune-related adverse effects during or after immunotherapy is essential.