Catechin is a naturally occurring polyphenolic compound found in plants such as, green tea, black tea, black grapes, apricots, broad beans, and strawberries. Catechins include, epicatechin, epigallocatechin, epicatechin gallate, epigallocatechin gallate, gallocatechin, catechin gallate, gallocatechin gallate, and catechin. These compounds exhibit notable biological activities such as anticancer, anti-inflammatory, antioxidative, antibacterial, and antifungal activities. This chapter includes catechin functionalized nanoparticles (NPs) that are synthesized employing various strategies such as precipitation, chemical reduction, and hydrothermal methods. Gold, silver, zinc oxide, and iron oxide nanoparticles showing exotic structural and functional properties after functionalizing with various catechins are elaborated. The resulting nanocomposites are characterized using advanced analytical techniques such as UV-vis spectroscopy, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), dynamic light scattering (DLS), Zeta potential measurements, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). Further, the superior antimicrobial, anticancer, antioxidant, and other therapeutic properties of the catechin functionalized NPs are also covered. Thus, the combination of catechins and nanomaterials can result in promising biomedical applications.