A 4.5-month-old baby girl presented to hospital with a 2-day history of watery diarrhea and fever. Rehydration and electrolytic balance were restored with intravenous fluid therapy followed by oral rehydration solution but diarrhea did not improve by the fourth day of hospitalization despite treatment with a probiotic. The patient was next treated with gelatin tannate, a medical device recently marketed in Europe to control and reduce the symptoms of diarrhea in infants, children, and adults. The child's diarrhea improved considerably within the first twelve hours and resolved completely within three days. Gelatin tannate might be considered as a useful treatment complementary to oral rehydration solution for the treatment of diarrhea in infants with rotavirus gastroenteritis.