Although the development of metal nanoparticle catalysts for organic synthesis has been widely studied, the catalytic potential of "metal phosphide nanoparticles" has little been studied. Herein, we describe that nickel phosphide nanoparticles (Ni2P NPs) act as a highly efficient heterogeneous catalyst for the selective transformation of biofuranic aldehydes into diketones, which is a useful biorefining technology. The biofuranic aldehydes are hydrogenated in water without any additives, giving the corresponding diketones in high yields. The catalytic performance of Ni2P NPs demonstrated here is significantly different from conventional Ni(0) and NiO NPs, and other metal phosphide NPs, which show no activity, indicating the unique catalysis of Ni2P NPs. Spectroscopic analyses showed that bifunctional Ni2P NP catalysis combining their hydrogen-activating ability and surface acidity plays a crucial role, leading to the transformations of selective biofuranic aldehydes.