The objective of this study was to investigate the use of Pleurotus ostreatus (P. ostreatus) nano-particles (POMP) as a new nano-biosorbent to remove Mn(II) from aqueous solution. Scanning Electron Microscope (SEM), Energy Dispersive Spectrometry (EDS), Fourier Transform Infrared Spectrometry (FIR spectra), Small-angle X-ray Scattering (SAXS) were used to characterize the nano-biosorbent. Adsorption experiments were carried out by batch experiments to investigate the effects of different experiment parameters including pH of the solution, adsorbent dose, initial Mn(II) ion concentration and contact time on adsorption capacity of PONP. The adsorption equilibrium study exhibited that Mn(II) adsorption of PONP was better fitted by Langmuir isotherm model. The maximum Mn(II) adsorption capacity of PONP was 130.625 mg/g at 298.15 K, which was higher than many other adsorbents. Pseudo-second-order kinetic model was the best one to predict the sorption kinetics with a maximum adsorption capacity of PONP attained within 30 min. PONP showed great potential in wastewater treatment due to the high adsorption capacity. Crown Copyright (c) 2013 Published by Elsevier B.V. All rights reserved.