Hypothyroidism has been associated with cognitive decline. Considering the role that has been suggested for folic acid (FA) in cognitive performance, the present study was designed to investigate the effects of FA against hypothyroidism-induced cognitive impairment, oxidative damage and acetylcholinesterase (AChE) activity alterations in propylthiouracil (PTU)-induced hypothyroid rats.In this study, PTU (0.05% in drinking water) and FA (5, 10, and 15 mg/kg, oral gavage) were administered to the rats for a period of 7 weeks. Then, behavioral performance was tested using Morris water maze (MWM) and passive avoidance (PA) tasks. Finally, oxidative stress indicators and AChE activity were assayed in the brain tissues.The impairing effect of hypothyroidism on cognitive performance was markedly alleviated by FA especially at the higher doses. In the MWM test, FA reduced escape latency and travelled distance, compared to the non-treated hypothyroid group. In the PA test, the latency to enter the dark chamber was signi cantly enhanced by FA as compared to the non-treated hypothyroid group (p < 0.05-p < 0.001).Besides, FA attenuated AChE activity and malondialdehyde level but increased superoxidase dismutase enzyme activity and total thiol content (p < 0.05-p < 0.001).In conclusion, FA could improve learning and memory ability in hypothyroid rats. The observed protective effects may be mediated through regulation of oxidative stress and AChE activity.