Received: December 2015, Accepted: January 2016Background: Pistachio is a plant that has long been cultivated in different parts of Iran. Pistachios are very nutritious and contain vitamins E and B, flavonoids, antioxidants, and carotenoids. Since the pistachio is effective in the treatment of some neurological disorders and is indigenous to Iran and considering the substantial use of this nut, it is necessary to investigate its effects on cognitive functions of the brain. This study aimed to investigate the effect of the hydroalcoholic extract of the pistachio on avoidance learning in rats. Materials and Methods: In this experimental study, 40 male Wistar rats (200-250 g body weight and 2-3 months of age) were divided into 4 groups. Dimethyl sulfoxide (DMSO) 2.5% (vehicle) and hydroalcoholic extract of the pistachio (10, 50, and 100 mg/kg/day) were administered by gavage for 14 days. Avoidance learning test was performed using the shuttle box. Results:The results of this study indicated a significant increase in the latency to enter the dark room in the groups receiving different doses of pistachio extract compared to vehicle treated group. Moreover, in the treated groups, time spent in the dark room was decreased compared to the vehicle group. The comparison of different doses of pistachio extract demonstrated that 100 mg/kg was more effective than 10 and 50 mg/kg of the extract. Conclusions:The results of this study indicated that treatment of rats with pistachio extract, which is rich in vitamins, flavonoids, and antioxidant compounds, can improve learning and memory.