Melanoma Antigen Genes (MAGE) are expressed in a broad range of cancers, including multiple myeloma. MAGE have been under investigation for more than 3 decades as targets for immune therapy, while in parallel, interrogation of their functions has revealed activities that may be particularly critical in multiple myeloma. MAGE-C1 is expressed in about 75% of newly diagnosed cases and this is maintained through the natural history of the disease. In contrast, MAGE-A3 is expressed in about 35% of newly diagnosed cases, but this increases to more than 75% after relapse. MAGE-A3 expression was associated with poor clinical outcome and resistance to chemotherapy. Translational studies have revealed that MAGE-A3 regulates cell cycling and apoptosis in myeloma cells. Genomic, gene expression, and multiomic studies demonstrate relations with high-risk subgroups of patients. MAGE-A3 mediates these functions through partnership with Kap1 to form a ubiquitin ligase complex. Structural analysis of the interaction between MAGE-A3 and Kap1 gives insight into the biochemical activity and substrate specificity and suggests novel pharmacologic strategies to inhibit them. These studies demonstrating MAGE-A3 oncogenic functions suggest that it may also be a suitable target for small molecule inhibition in multiple myeloma that may be broadly applicable to other cancers that express it.