Over 160 therapeutic and diagnostic monoclonal antibodies have been approved by the US FDA since the first monoclonal antibody, muromonab, was approved in 1986. Approximately 42% of these approvals were for the treatment or diagnosis of oncology indications, although some products are no longer marketed. This review will look at the history of monoclonal antibody development and approvals, discuss current antibody-based modalities, regulatory considerations for engineering approaches, critical quality attributes for different modalities, immunogenicity of mAbs across oncology products, and the future directions for development of therapeutic and diagnostic monoclonal antibody-based products.