To analyze the clinical characteristics and prognosis of adenovirus infection after allogeneic hematopoietic stem cell transplantation. A total of 26 patients with adenovirus infection admitted to the posttransplant ward of the First Affiliated Hospital of Soochow University from 2018 to 2022 were enrolled. Their data on baseline and clinical characteristics, treatment, and follow-up were analyzed. The median patient age was 30 (22, 44) years. Twenty-two patients received related haploid stem cell transplantation, three received unrelated stem cell transplantation, and one received umbilical cord stem cell transplantation. Antithymocyte globulin was included in the conditioning regimen in 25 patients. The median time of adenovirus infection was +95 (+44, +152) days. The median peripheral blood lymphocyte count was 0.30 (0.11, 0.69) × 10(9)/L. Twelve patients had acute graft-versus-host disease. Twenty-four patients received antirejection therapies at diagnosis. Sixteen cases had combined infection with other pathogens with adenovirus infection. Eight cases were diagnosed as asymptomatic infection, and 18 were diagnosed as adenovirus disease, including pneumonia (38.89% ) , gastrointestinal disease (38.89% ) , encephalitis (33.33% ) , hepatitis (5.56% ) , and urinary tract inflammation (5.56% ) . The age of >30 years was a risk factor for adenovirus disease (=0.03) . Eighteen patients received tapering of immunosuppression, and all 26 patients received at least one antiviral drug. Other treatments included high-dose gamma globulin and donor lymphocyte infusion. Adenovirus infection improved in 10 cases and progressed in 16 cases. The median follow-up time was 30 (7, 237) days. Twenty-two patients died. The all-cause mortality rate was (88.5±7.1) % , and the attributable mortality rate was 45.5% . There was no significant difference in the 100 d survival rate between asymptomatic infected patients and patients diagnosed with adenovirus disease (37.5% 22.2% , =1.83, 95% 0.66-5.04, =0.24) . The age of >30 years was a risk factor for adenovirus disease. Mortality was high in patients with adenovirus infection after allogeneic hematopoietic stem cell transplantation.