Cancer immunotherapy focused on monoclonal antibodies (mAbs) has emerged as a powerful tool in the armamentarium against tumors. In this regard, bispecific antibodies (BsAbs) are a revolutionary new pillar in cancer treatment. Indeed, BsAbs are a promising milestone in terms of increasing clinical therapeutic outcomes. BsAbs are engineered to target two distinct antigens. BsAbs have been designed within the framework of cancer therapy during the last several decades, particularly for treating hematologic malignancies and solid tumors. There are already more than a hundred distinct BsAb forms, and new ones are always being developed. In this chapter, we elaborate on the types of BsAbs and their structures based on different molecular platforms. This chapter also comprehensively focuses on the role of BsAbs in treating hematological neoplasms and common types of solid tumors. We hope that this chapter can provide basic concepts and new ideas for the readers.