Despite an increase in the coexistence of metabolic syndrome (MetS) and psychological disorders, together with their great impact on socio-economic burdens, no protective strategies that focus on these situations are available. Due to the role of oxidative stress in the pathophysiology of metabolic syndrome (MetS) and psychological disorders, we hypothesized that substances possessing antioxidant activity such as the novel functional ingredients from Anacardium occidentale (AO) could mitigate common psychological disorders in MetS rats. Male Wistar rats, weighing 200–250 g, were induced with MetS through a 12-week high-fat and high-cholesterol diet (HFHC). Then, they were given AO orally via a gastric gavage needle at doses of 1, 10 and 100 mg/kg BW for 14 days. Spatial memory, anxiety, depression, and sleep behaviors, together with changes in oxidative stress status and neurotransmitters, were assessed. All doses of AO significantly improved memory, anxiety, and sleep, together with the suppression of oxidative stress, AChE, and GABA-T in the cerebral cortex and hippocampus. These results suggest the protective effect of AO against anxiety, insomnia, and memory impairment that coexist with the MetS condition via an improvement in oxidative stress and the functions of the cholinergic and GABAergic systems. However, this benefit requires clinical confirmation.