Methods. The article presents a clinical case of convulsive syndrome in a 4.5-month-old child in the post-vaccination period. 8 hours after the administration of several vaccines, there were an increase in body temperature to 38.5°C, doubly loose stools. During the following two days condition of the child remained satisfactory, but on Day 3, despite overall well-being, seizure syndrome had occurred, lasting for four following days. During the hospital stay the seizures were observed while the body temperature remained normal and in the absence of electrolyte disorders. The sleep EEG, epileptiform activity was not detected on two occasions, and genetic testing for metabolic disorders returned negative. No structural brain changes were identified on the MRI scan and the ultrasound imaging. According to the results of PCR and ELISA studies, the etiology of the virus causing the disorder could not be determined. Conclusion. The described clinical case matches the characteristics of benign convulsions with mild gastroenteritis (CwG) in viral diarrheas, first described by Morooka in 1982. In subsequent years, this syndrome has been reported in association with various viral diseases; however, data on it remain limited in domestic literature. Given the insufficient awareness of pediatricians regarding this syndrome, through our clinical observation, we would like to draw attention to the discussion on this topic.