This article presents effects of polydispersity in polymers grafted on spherical surfaces on grafted polymer chain conformations, grafted layer thickness, and free-end monomer distribution within the grafted layer. At brush-like grafting densities, as polydispersity index (PDI) increases, the scaling exponent of radius of gyration of grafted chains approaches that of a single chain grafted on the same nanoparticle, because polydispersity alleviates monomer crowding within the brush. At high PDI, the chains shorter than the number average chain length, Nn, have more compressed conformations, and the chains longer than Nn overall stretch less than in the monodisperse case. As seen in polydisperse flat brushes at high grafting densities, the grafted layer thickness on spherical nanoparticle increases with PDI. Polydispersity eliminates the region near the surface devoid of free-end monomers seen in monodisperse cases, and it reduces the width of free-end monomer distribution and shifts the free-end monomer distribution close to the surface. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012