The nanocomposites of hollow and porous palladium nanospheres (Pd-HPs) supported on reduced graphene oxide (rGO) were prepared and then applied for electrochemical sensing of hydrogen peroxide (H2O2). Pd-HPs/rGO nanocomposites were synthesized for the first time through a facile one-pot hydrothermal route by using urea as the structure directing agent and reductant. The morphology and composition of the nanocomposites were characterized using transmission electron microscope (TEM), fourier transform infrared spectroscopy and energy-dispersive X-ray spectrum. TEM observations revealed that the as-synthesized PdHPs/rGO nanocomposites exhibited a sphere-shaped hollow and porous structure. The electrochemical investigations indicated that Pd-HPs/rGO nanocomposites exhibited excellent electrocatalytic performance toward H2O2 reduction with a linear range from 50.0 mu M to 9.25 mM, a high sensitivity of 216.2 mu A mM(-1) cm(-2) and a low detection limit of 9.5 mu M. (C) 2016 The Electrochemical Society. All rights reserved.