Background: Acute gastroenteritis causes millions of deaths annually among young children, mostly in developing communities. It is a common reason for hospital admission in inpatient medical wards. So, optimal nursing management is required for those children. Objective: This study aimed to investigate the effect of mothers' application of yogurt probiotic bacteria on relieving their young children's acute gastroenteritis. Design: A quasi-experimental research design was used to accomplish this study. Setting: This study was conducted at the inpatient medical ward for gastroenteritis in El-Raml Children's Hospital at Alexandria, Egypt from November 2022 to July 2023. The study was registered in ClinicalTrials.gov (NCT06090708). Subjects: A convenient sample of Sixty young children with acute gastroenteritis with no or some dehydrations were divided randomly into two equal groups; control and probiotic study groups. Methods: Characteristics and clinical data of children with acute gastroenteritis assessment record and assessment of children's diarrhea, vomiting and dehydration interview schedule were used to collect the necessary data. Study outcomes were evaluated before intervention and daily after intervention for three consecutive days for each child from their mothers. Children in control group received the standardized hospital care for acute gastroenteritis and children in probiotic study group received daily fresh yogurt with probiotics for three consecutive days beside to the standardized hospital care of acute gastroenteritis. Results: It was found that young children who received yogurt with probiotics bacteria exhibited less vomiting than other children in the control group through the study period. Besides that, the probiotic study group showed statistically significant improvement in diarrhea on third day of study compared to control group (P=.010). Further significant improvement was noticed related to the degree of dehydration for probiotic study group on second and third days of study compared to children in the control group (P= .021 &.002, respectively). It is concluded that the application of yogurt probiotic bacteria had a beneficial significant effect on young children with acute gastroenteritis on reducing its duration, frequency and severity of vomiting and diarrhea as well as improving severity of dehydration besides standardized care of hospital.