BACKGROUND Adenovirus infections are prevalent in children, typically presenting with mild or asymptomatic symptoms. However, some children develop severe pneumonia necessitating hospitalization. This retrospective study aimed to identify risk factors associated with severe adenovirus pneumonia in children. MATERIAL AND METHODS We screened consecutive children admitted for community-acquired pneumonia at the Emergency Department of Guangzhou Women's and Children's Medical Center between 2017 and 2019. Adenovirus infection was confirmed through rapid respiratory virus assay, RT-PCR assay from respiratory secretions, or serum IgM antibodies. According to Chinese guidelines, patients with pneumonia were classified into severe and mild groups. We assessed risk factors for severe adenovirus pneumonia by comparing clinical features and laboratory indicators, then included differing factors between the 2 groups in a logistic regression analysis. Data analysis was performed using SPSS 26.0 software. RESULTS Our study included 173 children diagnosed with adenovirus pneumonia (117 severe, 56 mild). The median age was 40 months, with 64 male patients. Univariate analysis and binary logistic regression analysis revealed that pleural effusion (13.449 [1.226-147.510], p=0.033), electrolyte disturbances (15.149 [2.724-84.246], p=0.002), oxygen therapy (258.219 [20.684-3223.548], p<0.001), bronchoscopy (26.781 [6.088-117.805], p<0.001), and steroid administration (6.584 [1.497-28.953], p=0.013) were associated with the severity of adenovirus pneumonia. CONCLUSIONS This single-center retrospective study identified pleural effusion, the need for bronchoscopy, oxygen therapy, and steroid treatment, along with impaired serum electrolytes, as factors associated with severe adenovirus pneumonia in children.