One of the deadliest features of most malignant tumours is the capacity of cancer cells to avoid being targeted by the immune system. The majority of cancer-related morbidity and mortality are caused by cancer metastasis. Conventional approach to treating cancer has relied on either destroying or removing cancer cells in the tumour by radiation, surgery, and rather non-selective chemotherapy. For generations, the goal of medicine has been to create medications that can kill cancer cells only, and immunologic strategies have been explored as a means of achieving this goal. Over the past few decades, the development of recombinant antibody technology and the realisation of antibodies’ clinical utility have made antibody therapeutics the largest and fastest-growing class of drugs that offer major health advantages to patients. These benefits are particularly evident in the treatment of cancer patients, as antibody therapies stimulate the defence system of the body to specifically eradicate cancerous cells. Numerous antibody-based treatment approaches have been created, and monoclonal antibodies have had encouraging outcomes in both preclinical and clinical trials. Today, monoclonal antibody-based immunotherapy is regarded as an essential part of cancer treatment, in addition to chemotherapy, radiotherapy, and surgery. Besides their immense therapeutic potential, monoclonal antibodies have recently shown to have a wide range of clinically significant modes of action. Furthermore, antibodies have the ability to specifically target tumour cells while also encouraging the development of durable immune responses against cancer. The many qualities of antibodies as a therapeutic platform have prompted the creation of fresh approaches to cancer treatment that will dramatically alter the way cancer is treated. Nevertheless, monoclonal antibodies are also linked to particular toxicities, which calls for additional research in order to create novel protocols for anticipating and managing adverse effects. Furthermore, improved comprehension of the insights gathered from lab research and clinical trials may help advance cancer treatments. This chapter outlines the known mechanisms of action, present clinical application treatment of cancer, mechanism of resistance of monoclonal antibody therapy, adverse events with monoclonal antibody therapy, combination therapies, and regulatory requirements.