Silver nanoparticles (AgNPs) are well-known nanomaterials that have been mainly used as antimicrobial agents Hundreds of chemical or biological methods have been reported and described for the preparation of AgNPs in water so far. Aqueous colloids of AgNPs normally have a limited capacity to safely change to the concentrated form using conventional methods such as different evaporation methods. Organic solvents which could be easily evaporated using conventional evaporation vacuum methods are good candidates for the preparation of highly concentrated AgNPs formulations or dried concentrates. In this study, we used a previously described biological method for preparing AgNPs in an acetone-water solvent mixture. The nanoparticles were synthesized using culture supernatant of Klebsiella pneumonia in the above organic solvent mixture supplemented with polyethylene glycol 6000 in a bright condition and subsequently dried by a conventional evaporation method. In the next step, dried residues were re-dispersed in water under ultra-sound treatment and characterized with different instrumentation methods. The results showed spherical AgNPs with a size range of ≤ 200 nm. This is the first report on the biological synthesis of AgNPs in an organic solvent mixture which could be easily converted to a dried form. This dried AgNPs concentrate is a good candidate for the preparation of very thick formulations of AgNPs such as solid or semi-solid pastes.