Antimicrobial agents and corrosion inhibitors are widely used as biocides in the oil and gas industry to disinfect the water and inhibit excessive biofilm formation and microbial induced corrosion (MIC) caused mainly by sulfate reducing bacteria (SRB). However, traditional biocides may induce bacterial resistance and/or be detrimental to environment by forming harmful disinfection byproducts. A chitosan-based nanocomposite is successfully implemented as a novel green biocide for treatment of water, the inhibition of sulfate reducing bacteria (SRB) and reduction of biocorrosion on SS400 carbon steel.