Currently the main sources of energy which are used for various human activities are fossil and nuclear fuels. However due to many parameters affecting these two types of fuels such as environmental concerns and limitations in resources, governments and scientist are paying much attention to new alternative sources of energy especially to those methods with dual applications such as microbial fuel cells (MFC). These cells can be utilized for both organic waste treatment and electrical energy production. In this study, a series of experiments were performed to investigate the effect of addition of nano silver particles to catholyte (cathodic solution) of an MFC on power generation. There are many different designs and configurations for MFCs. For purpose of this study a two chamber batch operated microbial fuel cell consisting of a cathode and an anode chamber, which were separated by a proton exchange membrane (PEM) was set up. Anolyte (anodic solution) consisted of 400 ml of a prepared solution which contained appropriate amounts of glucose (as substrate) and other needed supplements for bacterial growth and pH adjusters in addition to bacteria ( E.Coli O78:K80) which was prepared with appropriate procedures including inoculation and incubation. After the first run, subsequent experiments were carried out using the bacteria of previous runs utilizing electrochemical activation of bacteria. Catholyte in pure case consisted only of pure deionized water with bubbling air into it to provide oxygen for completion of the reaction at cathode. Experiments were performed using two types of electrodes consisting of carbon paper and carbon cloth. In each experiment anode and cathode were of similar type. For each type of electrode five experiments carried out: one without nano silver particles, and four with 1, 5, 10, and 15 ppm concentrations of nanoparticles. Duration of each cycle of fuel cell operation was about 25 to 30 hours. In these experiments first measurable increase in power generation was recorded at 5 ppm concentration of nanoparticles. This increase continued with increase of concentration up to 15 ppm. For carbon paper electrode, at 15 ppm concentration an 18% increase in maximum current and 26% increase in maximum power relative to case without nanoparticles was observed. For carbon cloth electrode same trend was observed with 19% and 29% increases for maximum current and power respectively. Further investigations on catholyte by voltammetry, and conductometry verified the positive effects of nano silver particles. Also transmission electron microscopy (TEM) photographs of electrode surfaces showed binding of nanoparticles on the surface. In addition to effect of presence of nanoparticles in catholyte, mixing effects in both cathode and anode chambers were investigated. At a fixed nanoparticles cboth