An autopsy of spiral wound reverse osmosis (RO) membrane operated in brackish water treatment was conducted to understand the origin and extent of foulants and fouling mechanisms. Structural and chemical characterization was determined by visual inspection and instrumental analysis such as scanning electron microscopy/energy-dispersive X-ray spectroscopy (SEM-EDS) and X-ray diffraction (XRD). It was observed that the membrane surfaces were completely covered with a gray/brown pollutant layer in all membrane sheets. SEM images proved accumulation of mineral pollutants on membrane surface. Also, high levels of Al and Si, which were attributed to aluminum silicates originating from feed water, were determined on membrane surfaces. Additionally, the XRD analysis results showed that the foulant sample collected from membrane surfaces included halloysite, SiO2 and LiCl components. Fujiwara's result proved that no damage occurred on the membrane surface due to oxidation. Consequently, a fouling control strategy for RO-based brackish water treatment plants was also recommended to increase the membrane life.