Aim: The aim of this study is to compare the dosage-related effects of levetiracetam and valproic acid on neural tube defect formation in chick embryos, when applied as monotherapy and in combination. Material and Method: A total of 360 fertilized pathogens-free white-Leghorn eggs were used in the study. The eggs were allowed to incubate for 72 hours. Total of six groups were formed where each medication was administered in low (250 mcg) and high (500 mcg) doses and in combination. Results obtained from the control and sham groups were compared. Results: The prevalence of NTD was found to be significantly lower in the group that received levetiracetam compared to the group that was treated with valproic acid. It was determined that NTD prevalence increased with a dosage increase in both groups. The prevalence of NTD was found to be significantly higher in groups where the two medications were administered in combination compared to the groups that received a single medication. Discussion: Both levetiracetam and valproic acid have the potential to create NTD. Valproic acid has a higher potential of creating NTD compared to levetiracetam. The likeliness of causing NTD significantly increases depending on dosage for both medications. Both medications have the potential to create NTD during pregnancy and must be used with caution.