Bispecific antibodies, engineered to simultaneously bind two distinct antigens or two epitopes on the same antigen, are now widely utilized in tumor therapy and various other fields. Depending on their mechanisms of action, bispecific antibodies can be designed into diverse structural formats, including IgG-like bispecific antibodies containing an Fc region. The Fc region mediates immune effector functions by interacting with receptors on immune cells or soluble immune components. However, antibodies containing an Fc region have a relatively high molecular weight, which limits their tissue penetration. They also exhibit slow systemic clearance in vivo and possess pharmacokinetic characteristics marked by a long terminal elimination half-life. Symmetric IgG-like bispecific antibodies feature a symmetric structure and are bivalent for each target antigen. During production, since the two heavy chains carrying the Fc region are identical, issues related to chain mispairing do not arise, thereby simplifying the manufacturing and purification processes. Moreover, the pairing of two identical natural Fc chains allows for correct disulfide bond formation, resulting in a more stable structure. Glycosylation of the Fc region remains in its natural state, preserving Fc-mediated functions. However, as the variable regions of the two antigen-binding sites are linked to the same heavy chain, the design must account for potential steric hindrance when the antibody binds both antigens simultaneously. In contrast, asymmetric IgG-like bispecific antibodies consist of two different heavy chains, each carrying antigen-binding domains that recognize distinct antigens or epitopes, offering greater structural design flexibility. Their development, however, requires addressing challenges related to heavy chain and light chain pairing. Strategies to prevent heavy chain mispairing include engineering the spatial configuration of the Fc region, facilitating Fab arm exchange, applying IgG-IgA chain exchange techniques, and introducing charge modifications in the Fc domain. To ensure correct light chain–heavy chain pairing, approaches such as introducing electrostatic interactions or novel disulfide bonds between the chains, swapping the CH1 and CL domains, or replacing the CH1-CL module with a T-cell receptor-derived structure have been employed. Non-IgG-like bispecific antibodies lack an Fc region. They are characterized by their small size and low molecular weight, which confer enhanced tissue penetration, rapid systemic clearance, and high structural versatility. Unlike IgG-based formats, they do not bind Fc receptors or activate the complement system directly. Different bispecific antibodies exert therapeutic effects through distinct mechanisms, which are largely determined by their structural design and target specificity. Currently recognized mechanisms of action include T cell redirection, dual signaling pathway blockade, immune checkpoint inhibition, formation of ternary complexes by binding two molecules, neutralization of soluble ligands, and acting as cofactors to mimic or enhance biological processes. Bispecific antibodies are extensively applied in cancer therapy. Beyond oncology, they are also being developed for the treatment of autoimmune diseases, infectious diseases, hematological disorders, and other conditions. Different structural designs offer unique advantages across therapeutic areas. This article elaborates on the structural designs of various types of bispecific antibodies and reviews their mechanisms of action and applications in therapeutics.