De novo urothelial carcinoma is relatively rare among post-transplant malignancies and never reported in pediatric kidney transplant recipients. In this paper, we reported one 12-yr-old male case with painless gross hematuria as the initial manifestation of de novo urothelial carcinoma in living donor graft pelvis. We emphasize the importance that cystoscopy and retrograde pyelography of native and transplant kidneys should be performed in all kidney transplant recipients with painless gross hematuria.