Using the extracellular fungal proteins, a low cost and eco-friendly synthesis of zinc oxide nanoparticles has been demonstrated in aqueous solvent system. The obtained nanoparticles were characterized by transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), UV-visible spectroscopy and powder X-ray diffraction (XRD) measurements. The as-synthesized particles were quasi-spherical, symmetrical, polydisperse and well distributed without any aggregation with size predominantly ranging between 80 and 120 nm. Photoluminescence (PL) and fourier-transform infrared (FT-IR) spectroscopy studies revealed that nanoparticles were individually coated with protein molecules that may act as stabilizing agents. Photocatalytic studies for the degradation of methylene blue dye under UV irradiation revealed extremely high photocatalytic activity of protein-capped ZnO nanoparticles (nearly 90% degradation in 30 min) which clearly outperformed commercial bare ZnO nanoparticles (nearly 40% degradation in 30 min) under the same conditions. The remarkable photocatalytic performance originated mainly due to the presence of surface proteins which act as an effectual host for methylene blue dye and facilitates absorption of dye along with low recombination rate of the e(-)/h(+) pairs. The low cost, simplicity and eco-friendly nature of the present protocol for "one-pot" synthesis and modification of ZnO nanoparticles could be extended to synthesize other metal nanoparticles thus expanding its applicability in various fields. (C) 2013 Elsevier B.V. All rights reserved.