3,4-dihydroxyphenethylamine (dopamine) is a neurotransmitter that has vital functions in the nervous system. Dopamine metabolism and reactive oxygen species (ROS) production are highly related processes. The present study aims to evaluate the effects of walnut (Juglans regia L.) extract (WE) and 5-hydroxy-1,4 naphthoquinone (juglone) on dopamine levels and oxidative stress. For this purpose, WE and juglone were administered to rats. Serum and brain dopamine levels, total oxidant status (TOS), and total antioxidant status (TAS) were measured after 21 days. The oxidative stress index (OSI) was calculated. WE (300 mg/kg) significantly increased brain dopamine levels. WE and juglone reduced oxidative stress in liver and brain tissues compared to serum. Our results revealed that WE and juglone might have a neuroprotective effect. Further studies are needed to extensively investigate the molecular mechanism of the effects of herbal extracts and phenolic compounds on brain health. Display omitted •Walnut extract increased the level of brain dopamine in rats.•Walnut extract and juglone reduced oxidative stress in brain and liver tissues.•Herbal extracts and secondary metabolites with phenolic character could be beneficial effects on brain health.