This work was conducted to study oral acute toxicity study of Phyllanthus acidus leaves and its action on the central nervous system (CNS) because no data in the literature have been found about of pharmacological activity of this plant in the CNS. In the present study aqueous extract of phyllanthus acidus leaves (Phyllanthaceae) was tested orally in swiss albino mice at doses of 100 mg/kg, 200 mg/kg and 400 mg/kg b.w. For CNS related activities significant central nociceptive activity was observed.