Formaldehyde is ubiquitous in the environment. It is known to be a genotoxic substance. We hypothesized that reactive oxygen species (ROS) and lipid peroxidation are involved in formaldehyde-induced genotoxicity in human lung cancer cell lines A549. To test this hypothesis, we investigated the effects of antioxidant on formaldehyde-induced genotoxicity in A549 Cell Lines. Formaldehyde exposure caused induction of DNA–protein cross-links (DPCs). Curcumin is an important antioxidant. Formaldehyde significantly increased malondialdehyde (MDA) levels, and decreased superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity. In addition, the activation of NF-κB and AP-1 were induced by formaldehyde treatment. Pretreatment with curcumin counteracted formaldehyde-induced oxidative stress, ameliorated DPCs and attenuated activation of NF-κB and AP-1 in A549 Cell Lines. These results, taken together, suggest that formaldehyde induced genotoxicity through its ROS and lipid peroxidase activity and caused DPCs effects in A549 cells. Copyright © 2012 John Wiley & Sons, Ltd.