Congenital renal anomalies, Williams Syndrome and non-Hodgkin lymphoma all occur separately at low incidence, so their simultaneous presence in the same patient is exceptional. We present a young patient manifesting all three conditions. This child is a boy with a Williams Syndrome phenotype who was diagnosed with severe chronic kidney disease secondary to bilateral renal dysplasia/hypoplasia. Due to his small size, he received treatment with growth hormone. He progressed to end stage kidney disease and, after 8 months, a renal transplant was performed. A number of suspicious abdominal adenopathies were removed during the surgery and, thereafter, immunosupressive treatment with prednisone, azathioprine and cyclosporine was initiated. Examination of the biopsy tissue confirmed the presence of a T-cell lymphoblastic lymphoma. Appropriate chemotherapy was given, and the immunosupressive regimen was eventually reduced to prednisone alone. Now, 8 years since the initial diagnosis of T-cell lymphoblastic lymphoma and 6 years after the completion of the chemotherapy, the patient is still in complete remission with a functional donor kidney. We discuss some possible explanations of this association. Chemotherapy has not appeared to have affected the viability of the grafted kidney and, in fact, it may even have induced immunotolerance.