Background: Infectious diarrhea is a common gastrointestinal disease in children, necessitating timely and effective therapeutic interventions. Rational rehydration and electrolyte replacement, elimination of causative agents, and zinc supplementation are crucial measures to prevent complications and reduce mortality. Objectives: To identify the characteristics and rate of rational drug use in the treatment of infectious diarrhea in pediatric inpatients under 5 years old. Materials and methods: A retrospective cross-sectional descriptive study was conducted on 192 medical records to identify drug use characteristics and to evaluate the rationality of drugs used for infectious diarrhea treatment based on criteria such as substance selection, dosage, dosing interval, duration, and route of administration. Results: Antibiotics were prescribed in 93.23% of cases, with cefixime being the most frequently used antibiotic (29.8%). Antibiotic combinations accounted for 6.7% of total prescriptions, with the combination of cefotaxime and tobramycin being the most common (50%). Rehydration was indicated in 73.96% of the cases, in which intravenous fluids were the most common choice (69.79%). The rate of rational antibiotic prescribing was 67.60%, while the rate of rational rehydration and electrolyte replacement was only 24.62%. Conclusion: The use of drugs for infectious diarrhea treatment at the hospital needs to be optimized according to standard treatment guidelines, especially regarding antibiotic selection and fluid therapy, contributing to ensuring patient safety and effectiveness.