Nigella sativa, an endogenous plant of family Ranunculaceae exhibits a wide range of biological activity. This experiment on the anticonvulsant effects of aqueous Nigella sativa seed extract (NS) was studied using pentylenetetrazole (PTZ - 40 mg/kg b.w.) induced seizure model on adult albino Holtzman rats. The control group rats received normal saline whereas the experimental group rats were treated with NS. The effects of NS on motor behaviour, sleeping time, seizure parameters (ictal phase duration, interictal phase duration, seizure score) and EEG were studied. The results indicated that NS impaired motor coordination, reduced locomotor activity but increased sleeping time. It also showed the animals with prior treatment with NS to have much resistance to convulsion than the control animals. Ictal phase duration and severity score decreased whereas interictal phase duration and duration of onset of seizure increased in NS treated group. In EEG recording spike/wave and burst discharges were reduced considerably after NS treatment. Picrotoxin, a GABAA antagonist antagonized the reduction of seizure activity by NS, inhibited the prolongation of seizure latency. The above results suggest that NS may have anticonvulsant activity in the petit mal epilepsy probably through an increase in GABAergic tone. © Society of Integrated Sciences • International Medart.