Catamenial epilepsy is one of the most important neurological diseases in women during menopausal cycle. Apium graveolens L. has various therapeutic properties in epilepsy but its effectiveness in convulsions during estrus cycle. Thus this study aimed to determine antiepileptic effect of the celery essential oil during estrous cycle in pentylenetetrazol (PTZ)-induced seizures in rat. Thirty female Wistar rats were divided into 5 experimental groups as control, sodium valproate (75 mg/kg), celery essential oil (40, 80 and 160 mg/kg) each with four subgroups (proestrus, estrus, metestrus and diestrus). Puberty was decided by vaginal smears and animal with two normal cycles were chosen. After administration of the sodium valproate or celery essential oil, PTZ injection (80 mg/kg, i.p) was done. Animals were observed for 30 min and initiation time of myoclonic seizures (ITMS), initiation time of tonic–clonic seizures (ITTS) and seizures duration (SD) were registered. According to findings, celery essential oil (160 mg/kg) significantly increased the onset time of ITMS and ITTS compared to control group (P<0.05). Also, celery essential oil (160 mg/kg) significantly decreased SD compared to control group (P<0.05). Also, antiepileptic effect of celery essential oil was significantly more prominent during luteal phase than follicular phase (P<0.05). These findings suggest that celery essential oil has antiepileptic role which is more prominent during luteal phase than follicular phase.