Membrane degradation due to biofouling is one of the main obstructions for aromatic polyamide thin film composite (TFC) reverse osmosis (RO) membranes to realize high performance over a long period of operation. In this study, thin film nanocomposite (TFN) membranes consisted of silver nano particles as the anti bacterial material and poly (vinyl pyrrolidone) as the hydrophilic polymer with antibacterial ability was devised as a novel means to mitigate membrane biofouling. The sliver nanoparticles were synthesized by sonochemical method by applying ultrasonic irradiation to the aqueous solutions of sliver nitrate as the precursor silver colloids, meta phenylene diamine monomer as reducing agents and poly (vinyl pyrrolidone) powder as stabilizer. The effects of the synthesis conditions such as molar ratio, time and temperature reduction on the size and shape of the particles were also studied. Formation and size of the silver nanoparticles were investigated by using UV–Visible spectroscopy and Atomic Force Microscopic methods. The results showed that average particle size of the silver particles varied between 55 to 520 nm. The smallest particles were obtained from a synthesis solution initially contained 0.4% (w/v) nitrate silver, 2% (w/v) meta phenylene diamine, 1.85% (w/v) poly (vinyl pyrrolidone) which was reduced at 10 ?C for 15min. The thin film nanocomposite membranes were prepared via in situ interfacial polymerization of trimesoyl chloride (0.2% (w/v)) in the hexane solvent and colloidal silver solution over porous polysulfone micro filtration supports. Attenuated total reflectance mode Fourier transform infrared (ATR-FTIR) spectroscopy showed that the thin film nanocomposite membrane had three characteristic bands at 1541, 1602 and 1649 cm - 1 corresponding to amide and carbonyl groups in polyamide. This resultuggestedthat the thin film nanocomposite membranes were synthesized in the presence of nano silver and poly (vinyl pyrrolidone). The top surface morphology of thin film composite and silver-polyamide membranes was analyzed by scanning electron microscopy (SEM). Comparison between the SEM images of the surface morphology of thin film composite and thin film nanocomposite membranes showed the thin film composite membrane had dense structure. However, the top surface morphology of thin film nanocomposite membrane is changed to open pore morphology by adding silver nanoparticles and poly (vinyl pyrrolidone) to the aqueous phase during synthesis process of the membranes. The EDX spectrum for thin film nanocomposite membrane showed elemental silver peak, confirming the presence of the silver element in the thin film nanocomposite membrane. The reverse osmosis performance of membranes exhibited that water permeation flux increased from 12 (l/m 2 h) for thin film composite membrane to 15 (l/m 2 h) for thin film nanocomposite membrane. Also salt rejection of thin film composite membrane decreased from 89% to 84% compared to thin film nanocomposite membrane. Finally, the results of measuring the thin film nanocomposite membrane resistance against the E. coli bacteria cell showed that the 75 % of the bacteria were destroyed which was much higher than 9% for thin film composite. Also thin film nanocomposite membranes proved to have more resistantagainst biofouling. Keywords: Nanosilver, interfacial polymerization, polyamide reverse osmosis membrane, antibacterial, biofouling