In the presence of poly(vinylpyrrolidone) and I-, uniform Pd nanowires and nanorods have been successfully prepared. As-prepared one-dimensional Pd nanostructures have a 5-fold twinned structure. The twinned Pd nanowires can be further transformed into nanowires/nanorods with a smaller aspect ratio and finally to multiply twinned particles upon increasing the reaction time. With structural anisotropy, the one-dimensional. Pd nanostructures exhibit different chemical reactivities on their tips and sides.