Adenovirus infections impose a significant disease burden on children and can result in poor clinical outcomes, thus requiring intensive care and potentially leading to fatality. We retrospectively analyzed pediatric adenovirus cases from 2018 to 2023 at a children's hospital in Taiwan and collected data regarding patients' clinical symptoms, imaging results, and laboratory findings. Multiple logistic regression was used to identify predictors of severe cases requiring intensive care. Our study revealed that adenovirus cases were more common in the winter, with a post-COVID-19 surge observed in 2023. A total of 576 pediatric adenovirus cases were collected, including 27 (4.7%) severe cases and 3 (0.5%) fatal cases. Severe cases were younger and exhibited higher frequencies of dyspnea, decreased activity, and diagnoses of bronchopneumonia/pneumonia and genetic disorders. Compared with nonsevere cases, severe cases also demonstrated more patchy opacity, lobar consolidation, pleural effusion, and bacterial coinfection. Multivariable analysis revealed that the most significant predictors of severe cases were dyspnea (aOR 18.5 [95% CI 3.792-90.257]), patchy opacity (3.391 [1.150-9.994]), lobar consolidation (116.388 [8.555-1583.393]), pleural effusion (9.117 [0.917-90.630]), and invasive bacterial coinfection (60.469 [4.047-903.555]), which are newly recognized predictors, thus highlighting the need for increased clinical vigilance.