Here we review the role of Galectins in the molecular pathogenesis of multiple myeloma and ovarian cancer, with a special focus on Glectin-3. Multiple myeloma is the second most common hematologic malignancy worldwide. Because the pathogenesis of multiple myeloma is still incompletely understood, there is no ultimately effective cure, and this cancer results fatal. Ovarian cancer is the most lethal gynecologic malignancy worldwide. Due to the lack of screening techniques for early detection, patients are mostly diagnosed with advanced disease, which results ultimately fatal. Multiple myeloma and ovarian cancer have different biologies, but they share a strong dependence on adhesion with extracellular matrix and other cells. Galectin-3 plays a key role in regulating such adhesive abilities of tumor cells. Here we discuss the outcomes and possible mechanism of action of a truncated, dominant negative form of Galectin-3, Galectin-3C, in these malignancies. Overall, we report that Galectin-3C is a promising new compound for effective adjuvant therapies in advanced, refractory multiple myeloma and ovarian cancer.