Ortho-phenylphenol (OPP) has been found to cause carcinomas in the urinary tract of rats. Since OPP is a potent genotoxic compound, and used as fungicides and antibacterial agents in fruits and fruit products, search for newer, better agents for protection against toxicity of OPP is required. In this study, the chemoprotective effect of hydroxytyrosol (HT) against OPP-induced DNA damage in HepG2 cells was investigated. Comet assay was used to detect the DNA damage induced by OPP. To elucidate the possible mechanisms, we tested lysosomal membrane stability, mitochondrial membrane potential, intracellular generation of reactive oxygen species (ROS), and reduced glutathione (GSH). Results showed that HT significantly reduced the DNA strand breaks caused by OPP. Moreover, HT effectively suppressed OPP-induced ROS formation, and increased the GSH level. Lysosomal membrane and mitochondrial membrane were also protected when cells were pretreated with HT. These results suggested that the disruption of lysosomal membrane integrity and the oxidative stress, leading to DNA fragmentation, may be the mechanism of DNA damage induced by OPP. The antioxidant activity of HT may play an important part in attenuating the DNA damage of OPP.