In Rosai-Dorfman disease (RDD), exclusive extranodal involvement with lesions limited to the kidneys is very uncommon and has been described only in adult patients. Occasionally, human herpesvirus 6 (HHV-6) has also been detected in RDD tissue samples. We present the case of a 7-year-old boy referred to our center presenting a single solid mass in the right kidney measuring 3.4 cm, detected both on contrast computed tomography and magnetic resonance imaging. Surgical excision was successfully completed, and the pathology report informed characteristic histopathology and immmunohistochemistry features of RDD. Human herpesvirus 6 was detected and amplified by polymerase chain reaction, as well as by immunohistochemistry. We discuss imaging and histology-based differential diagnoses in the pediatric age group. Although RDD is a rare histiocytic disorder of unknown etiology and pathogenesis, the presence of HHV-6 observed in this case supports the possibility of an abnormal immunologic response linked to viral presence.