Clinic report case of a kidney-transplanted female who, after one year of normal functioning, developed xantogranulomatous pyelonephritis in the renal allograft. Clinical presentation was mesorenal tumoration causing pyelocaliecstasis, which coincided with a progressive decline of renal function due to interstitial rejection. Diagnosis by eco-doppler imaging, CAT, arteriography, renogram and descending pyelography were non-specific in relation to the process benignant or malignant nature. Surgical examination with obtention of biopsy was not conclusive with regard to diagnosis and so, during a second surgery, transplanctectomy was chosen. The histological examination showed that the expansive process of the allograft corresponded to a case of xantogranulomatous pyelonephritis. After reviewing the existing literature, only 4 cases were found reporting this rare condition in a renal allograft.