Layered double hydroxidesLayered double hydroxides (LDHs) have gained significant attention in biomedical research owing to their biocompatibilityBiocompatibility, favorable cellular interactions, and versatile anion-exchange capacityAnion-exchange capacity. However, traditional Mg–Al-LDHs often lack the structural adaptability required to address the diverse and complex challenges of modern biomedicine. Incorporating transition metals (TMs) into the LDH framework provides an effective strategy to fine-tune physicochemical characteristics such as particle size, surface charge, and acid-base behavior. Moreover, TM–containing LDHs display advanced functionalities, including antimicrobial, photocatalytic, and luminescent properties. The transition-metal incorporation acts as additional design tool, complementing other approaches such as intercalation of therapeutic anions, surface functionalization with biomoleculesBiomolecules or nanoparticles, and integration with natural or synthetic polymers. Importantly, TM-LDHs offer multimodal activity, enabling combined functionalities for enhanced antimicrobial and anticancer therapiesAnticancer therapy, tissue engineering applications, and theranostic systems that unify diagnostic and therapeutic capabilities. The objective of this chapter is to discuss synthetic methodologies, property modulation, and functional enhancements achieved through TM incorporation, as well as their synergistic effects when coupled with other bioactive agents. Representative case studies emphasize the potential of TM-LDHs as multifunctional biomedical platformsBiomedical platforms. Nevertheless, future progress will depend on systematic and reproducible evaluation of their biocompatibilityBiocompatibility and therapeutic performance in both in vitro and in vivo models.