This paper describes the biosynthesis of core–shell CuO–Pd nanoparticles with the aid of a Cyperus rotundus rhizome extract. The crystallinity, surface chemistry, morphology and thermal properties of the synthesized nanoparticles were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and thermogravimetric analysis. The nanoparticles with Pd covered by a CuO enriched shell showed enhanced catalytic performance for organic transformations to synthesize 2,3-dihydroquinazolin-4(1H)-ones, spirooxindoles, and chromenylpyrimidin-2,4-diones in excellent yield. Moreover, the nanocatalyst can be recycled effectively for five consecutive reactions without significant loss of catalytic activity.