Ethanol extract of the roots of Nardostachys jatamansi DC. (Valerianaceae) was studied for its anticonvulsant activity and neurotoxicity, alone and in combination with phenytoin in rats. The results demonstrated a significant increase in the seizure threshold by Nardostachys jatamansi root extract against maximal electroshock seizure (MES) model as indicated by a decrease in the extension/flexion (E/F) ratio. However, the extract was ineffective against pentylenetetrazole (PTZ)-induced seizures. Nardostachys jatamansi root extract also showed minimal neurotoxicity against rotarod test at doses that increased the seizure threshold. Further, pretreatment of rats with phenytoin at a dose of 12.5, 25, 50 and 75 mg/kg in combination with 50mg/kg of Nardostachys jatamansi root extract resulted in a significant increase in the protective index (PI) of phenytoin from 3.63 to 13.18. The dose response studies of phenytoin alone and in combination with Nardostachys jatamansi extract on the serum levels of phenytoin clearly demonstrated the synergistic action of both the drugs.