Pd nanoparticles exhibit the abnormal behavior of the Pd lattice expanding as the size of the Pd nanoparticles decreases. We measured extended X-ray absorption fine structure of poly(N-vinyl-2-pyrrolidone)-protected Pd nanoparticles and confirmed that the Pd Pd bond distance in small Pd nanoparticles with a diameter of less than 3 nm was elongated by 2% compared with that in Pd foil. The origin of the unusual bond elongation was discussed.