Malathion is one of the most commonly used organophosphorous pesticides worldwide. Gold nanoparticles can be used for the degradation and removal of 10 ppm malathion. The morphology of the prepared gold nanoparticle is characterized by transmission electron microscopy. Photodegradation of malathion on irradiation to different light sources was monitored using different tools such as UV–visible spectra and high-performance liquid chromatography. Photodegradation rate of malathion was enhanced in the presence of gold nanoparticles as a result of surface plasmon phenomena.