We report a 20-month-old child with disseminated adenovirus infection after a haploidentical T cell-depleted stem cell transplantation. This case demonstrates the value of polymerase chain reaction surveillance for early detection of adenovirus infection and the role of quantitative polymerase chain reaction for monitoring antiviral therapy. It also emphasizes the importance of T cell immunity in controlling disseminated adenovirus infection after stem cell transplantation.