Abstract: Application of fungi in the biosynthesis of silver nanoparticles is a green and feasible alternative to chemical and physical methods used for AgNPs synthesis. The fungus Trichoderma reesei is a non-pathogenic and environmentally friendly microorganism capable to produce extracellular enzymes and metabolites in high scale. An extracellular biosynthesis of silver nanoparticles (AgNPs) from AgNO3 solution by using the cell-free extract of Trichoderma reesei biomass is presented in this study. Kinetics of the biotransformation is described by a second order reaction equation. Spherical or approximately spherical AgNPs that are well-dispersed and with a size between 3-4 and 15-17 nm have been produced at transformation degree of 30 % with respect to the initial silver ions concentration. The biosynthesized AgNPs show high stability against agglomeration even after storage for 60 days. Soluble xanthates, used in some industrial applications, are found toxic to aquatic biota even at low concentrations. The synthesized AgNPs are capable to immobilize potassium amyl xanthate from model wastewater. The pollutant adsorption is described by the Langmuir adsorption isotherm and the calculated maximum adsorption capacity is 4.67 mg/mg. The pollutant immobilization by AgNPs is much faster process and requires much less adsorbent (50 fold) in comparison with the activated carbon (chemical grade of purity).