Abstract Reactive oxygen species are one of the causative factors for the stress in post-mitotic cells. Mitochondria are the major source of the free radicals in the cells. In the present research work it has been aim to examine the effect of ethanolic extract of Petroselinum crispum (Parsley) leaves on the D-galactose induced oxidative stress in the brain regions of mouse. The activities of Lysosomal enzymes like Acid phosphatase & Non-specific esterase were measured in conjunction with lipid peroxidation in mitochondrial fraction of various regions of brain. A significant decrease in acid phosphatase & Non-specific esterase activity was observed in D-galactose stressed mice, whereas treatment of D-galactose with ethanolic extract of parsley group of mice showed protection against increased oxidative stress in all brain regions. Thus it is postulated that, parsley possess an antioxidant properties, that increases the level of enzyme activities in brain regions.