OBJECTIVE To study the clinical features of children with severe adenovirus pneumonia (SAP) and hemophagocytic syndrome (HPS). METHODS A retrospective analysis was performed from the chart review data of 30 children with SAP and HPS who were admitted from January 2014 to June 2019. According to the prognosis, the children were divided into a good prognosis group (n=18) and a poor prognosis group (n=12). RESULTS Among the 30 children with SAP and HPS, the ratio of male to female was 2:1. The median age of onset was 1 year and 3 months (range 3 months to 5 years), and the mean course of fever was 19±7 d. Of the 30 children, 28 (93%) experienced disease onset in January to June. High-throughput gene detection of serum pathogens showed that 16 (53%) children were positive for human adenovirus type 7 (HAdV-7), and the other 14 (47%) children were positive for HAdV antigen based on immunofluorescence assay for throat swab, with unknown type. Of all 30 children, 29 (97%) had respiratory complications, 24 (80%) had cardiovascular complications, 16 (53%) had gastrointestinal complications, and 9 (30%) had toxic encephalopathy. Eighteen children (60%) improved or recovered and 12 (40%) did not recover (3 died). Compared with the good prognosis group, the poor prognosis group had a significantly longer course from onset to diagnosis of HPS (P<0.05), significantly higher levels of fibrinogen and tumor necrosis factor-α (P<0.05), and a significantly lower level of interferon-γ (P<0.05). The mean follow-up time was 6±2 months; 11 (41%) children recovered, 1 (4%) experienced recurrence of HPS, and 15 (56%) had the sequela of post-infectious bronchiolitis obliterans (PIBO). CONCLUSIONS HPS may be observed in children with SAP, and PIBO is the most common sequela of SAP.