Introduction and objective: Acute gastroenteritis, a common childhood illness worldwide, manifests with symptoms including fever, abdominal pain, vomiting, and diarrhoea. It is highly contagious, with transmission occurring through contaminated water, food, or poor hygiene. Globally, 1.7 billion cases of diarrhoeal diseases are diagnosed annually, causing approximately 525,000 deaths among children under the age of five. Dehydration caused by diarrhoea is a primary cause of hospitalisation, particularly in developing countries. Aim: Analysis of the aetiology, frequency, and seasonal distribution of viral pathogens responsible for acute gastroenteritis in children hospitalised between 2019 and 2022 at the Military Institute of Medicine – National Research Institute in Warsaw, Poland. Materials and methods: Medical records of patients aged 0 to 18 diagnosed with rotavirus, norovirus, and adenovirus-induced acute gastroenteritis were analysed. The pathogens had been identified with reliable immunochromatographic tests. Exclusion criteria encompassed bacterial infections, dietary errors, and inflammatory conditions. Data examined included age, gender, aetiology of gastroenteritis, seasonality, duration of hospitalisation, and clinical symptoms (diarrhoea, vomiting, fever, abdominal pain, and dehydration). Laboratory results such as white blood cell count, C-reactive protein, electrolyte levels, and organ function markers were also evaluated. Results: Data from 350 children hospitalised between 2019 and 2022 were analysed. The highest number of hospitalisations occurred in 2019 and 2022, with fewer cases in 2020–2021, likely reflecting the impact of the COVID-19 pandemic. Most patients were between 6 and 12 months old. Rotavirus infection commonly presented with fever, vomiting, diarrhoea, and dehydration. Adenovirus and mixed infections were associated with slightly higher C-reactive protein levels, while rotavirus infections showed mildly elevated aspartate aminotransferase levels. Haematocrit, blood urea nitrogen, creatinine, and electrolyte levels were similar across all cases. Conclusions: Our analysis showed that rotavirus was the most frequent cause of acute viral diarrhoea in children, followed by norovirus and adenovirus, with mixed infections being the least common. The peak incidence occurred in autumn and winter, except in 2021, reflecting changes in the dynamics of infections related to the coronavirus pandemic. Biochemical findings were not sufficiently characteristic to infer the aetiology of the disease.