Adenoviruses are emerging as important viral pathogens in hematopoietic stem cell and solid organ transplant recipients, impacting morbidity, graft survival, and even mortality. The risk seems to be highest in allogeneic hematopoietic stem cell transplant recipients as well as heart, lung, and small bowel transplant recipients. Most of the adenovirus diseases develop in the first 6 months after transplantation, particularly in pediatric patients. Among abdominal organ recipients, small bowel grafts are most frequently affected, presumably due to the presence of a virus reservoir in the mucosa-associated lymphoid tissue. Management of these infections may be difficult and includes the reduction of immunosuppression, whenever possible, combined with antiviral therapy, if necessary. Therefore, an awareness of the pathology associated with such infections is important in order to allow early detection and specific treatment. We reviewed six transplant recipients (small bowel, kidney, and heart) with adenovirus graft involvement from two institutions. We sought to compare the diagnostic morphology and the clinical and laboratory findings. The histopathologic features of an adenovirus infection of the renal graft and one native kidney in a heart transplant recipient included a vaguely granulomatous mixed inflammatory infiltrate associated with rare cells showing a cytopathic effect (smudgy nuclei). A lymphocytic infiltrate, simulating T cell rejection, with admixture of eosinophils was also seen. In the small bowel grafts, there was a focal mixed inflammatory infiltrate with associated necrosis in addition to cytopathic effects. In the heart, allograft adenovirus infection was silent with no evidence of inflammatory changes. Immunohistochemical stain for adenovirus was positive in all grafts and in one native kidney. All patients were subsequently cleared of adenovirus infection, as evidenced by follow-up biopsies, with no loss of the grafts. Adenovirus infection can involve allografts as well as native organs in solid organ transplant recipients. Infection is associated with variable necrosis and acute inflammation, in addition to a rejection-like infiltrate. Hematuria in non-renal solid organ transplant recipients may be associated with adenovirus nephritis and clinically silent graft involvement. Prompt diagnosis (aided by immunohistochemistry (IHC) and serology), with specific treatment, can prevent graft loss.