Biofouling performance was evaluated for polyamide commercial RO membranes coated with iron nanoparticles (FeNPs) and graphene oxide (GO), under controlled conditions using a cross-flow system. Feed water obtained from the Sea of Cortez, Mexico, was pretreated, sterilized and inoculated with a high concentration (10(9) CFU mL(-1))of Bacillus halotolerans MCC1, isolated from the Sea of Cortez. The zeta potential was determined for FeNPs and GO-FeNPs. XRD, roughness, contact angle, permeance and flux were determined for the coated and uncoated membranes. To evaluate the anti-biofouling effect, total organic carbon, total cell count, optical density and percentage of live/dead cells were determined for the biofilm. The GO-FeNP coating showed less agglomeration tendency and surface roughness compared to pure FeNP, and contact angle (49.1 degrees +/- degrees 4.3) similar to the uncoated membrane (50.2 degrees +/- 4.3 degrees). Despite reducing the membrane permeance, the FeNP and GO-FeNP coatings presented larger fluxes after fouling (18% and 5.3% larger, respectively) than the fouled uncoated membrane. This was corroborated by both FeNP and GO-FeNP coated membranes presenting reduced biofilm layer thickness (89% and 65% thinner), total cell count (67% and 40% lower), optical density (40% and 48% lower) and total organic carbon (91% and 98% lower), than the uncoated membrane.