In this work, silver and copper particles of different nanoparticle precursor concentrations were decorated on the surface of thin film composite polyamide (TFC‐PA) reverse osmosis (RO) membranes by in situ method. The modified membranes were characterized by different techniques including Field emission scanning electron microscopy (FE‐SEM), X‐ray Absorption Spectroscopy (XAS), and attenuated total reflection – Fourier transforms infrared spectroscopy (ATR‐FTIR), water contact angle (WCA), and antibacterial capacity. After that, the membrane performance was compared through normalized flux and the possibility of the removal of bovine serum albumin (BSA) protein; the anti‐fouling and anti‐biofouling properties were also compared through the maintained flux ratios (%) after 5‐hour filtration. The used organic foulants were BSA protein and humic acid (HA) solutions. The results showed that, compared to the flux of the base, the flux of AgNPs‐decorated membrane can improve the separation ability up to 24% while that of CuNPs‐decorated membrane was 14%. The anti‐fouling property of decorated membranes was significantly increased compared to that of the base (from 64% for the base to over 77% for decorated membranes). Especially, the anti‐biofouling property of nanoparticles decorated membranes was also increased because of the higher maintained flux ratios (from 50% for the base to over 75% for decorated membranes). It indicates that this method can be applied to produce reverse osmosis (RO) membranes for reclamation wastewater with a high content of organic matter.