Renal involvement in non-Hodgkin lymphoma is a recognized development, but it mostly follows a diagnosis of lymphoma. We describe a rare case of a T-cell-type non-Hodgkin lymphoma that first presents as nephromegaly in a 5-year-old girl admitted to the emergency department with abdominal pain. Further investigation revealed bilateral nephromegaly, but the results of blood tests, imaging studies, and bone marrow aspiration were inconclusive. During the second week of hospitalization, significant physical examination revealed an enlarged lymph node in the anterior cervical chains, confirming a diagnosis of Non-Hodgkin's lymphoma. This case illustrates that it is important to have a high degree of suspicion in any patient presenting with unexplained enlarged kidneys without any identifiable cause because it could be the first presentation of a hematologic malignancy.