This work presents the synthesis of platinum and silver nanoparticles obtained on a support composed of the Slayer protein (SLP) isolated from Lactobacillus kefiri and polyurethane particles (PU). The support was obtained by adsorption of the protein on the polymer particles in aqueous dispersion. After combining the support with the platinum or silver salts and subsequently reducing with hydrogen, noble metal-based heterogeneous bionanocatalysts were obtained. Platinum or silver nanoparticles with diameters dn = 4.9 nm (ds = 4.9 nm; dv/dn = 1.05) or dn = 8.0 nm (ds = 10.6 nm; dv/dn = 1.63), respectively, were observed by TEM on the surface of the protein/polymer supports. Both nanocatalysts showed excellent catalytic activity in the reduction of p-nitrophenol with NaBH4 at room temperature, with conversions of 100% and 97% for platinum and silver bionanocatalysts, respectively. Noteworthy, both bionanocatalysts maintain their activity until 4 reuse cycles, being the platinum-based system the one showing the best performance. These results demonstrated that the developed bionanocatalysts are promising and emerging alternatives in the field of supported noble metal nanoparticlebased heterogeneous catalysts.