Background: Formaldehyde is widely used for industrial purposes and is also present in the nature in the polluted environment and atmosphere. Its exposure can cause health problems and seriously impact the central nervous system. Omega-3 fatty acids are well known for their neuroprotective properties. Aim of the work: This study was done to simulate occupational exposure to formaldehyde vapor. Also, it is designed to investigate its histopathological effects in the olfactory bulb of rats and possible protective effects of omega-3 fatty acids against these effects.Materials and Methods: Forty adult male albino rats were randomly allocated to four groups: control rats in Group I, rats in Group II were received orally omega-3 group (400 mg/kg for 4 weeks), rats in Group III were received 10 % formaldehyde vapor for 6 hours/day, 5 days/week for 4 weeks and rats in group IV were received formaldehyde plus Omega-3. At the end of the experiment, olfactory bulb sections were obtained and processed for light and transmission electron microscope study.Results: Formaldehyde treated group showed disorganized layers in the olfactory bulb with vacuolated surrounding neuropil. Disrupted glomeruli as well as loss of mitral neurons which appeared irregular, shrunken were demonstrated. Their nerve fibers showed splitting and irregularity of the surrounding myelin sheaths. Astrocytes immunoreaction showed a highly significant increase compared to the control groups. On the other hand, co-administration of omega-3 fatty acids improved most histological alterations in all layers of the olfactory bulb. In conclusion; exposure to Formaldehyde induced cellular damage to the olfactory bulb of rats. Co-administration of omega-3 showed marked protection at the cellular level and restoration of the ideal configuration of the olfactory bulb.