Background and Aim: There are contradictory data regarding the changes of corrected QT interval (QTc) in seizure. Regarding this, the present study aimed to evaluate the frequency of long QT syndrome (LQTS) in seizure patients without underlying cause in Hazrat-e Masoumeh Hospital, Qom, Iran. Materials and Methods: The present cross-sectional study was conducted on seizure patients without any underlying causes. The data were collected using a questionnaire covering such variables as age, gender, and history of seizure and syncope. Electrocardiogram (ECG) was obtained from the patients in the first 2 h after the occurrence of seizure. Moreover, the distance from the beginning of the Q wave to the end of the T wave in the lead limb II was measured by the researcher. Finally, the collected data were analyzed in SPSS software (version 22). Results: The participants consisted of 67 males (55. 8%) and 53 females (44. 2%) with the mean age of 6. 7±, 2. 1 years. Long QT was observed in five patients. The gender of the participants had no significant relationship with the type of seizure and family history of syncope, sudden death, heart disease, and seizure (P≥, 0. 05). The mean QT intervals in the males and females were 0. 40±, 0. 24 and 0. 40±, 0. 23 sec, respectively. Therefore, no significant difference was observed between male and female patients in this regard (P≥, 0. 05). Conclusion: Based on the results, LQTS in seizure patients without underlying causes was found in only five patients. However, in special cases, such as a family history of QTc disorders, history of suspected faint, and resistant or status epilepticus, the implementation of ECGs can be helpful for children.