Neurolymphomatosis refers to lymphoma that has infiltrated the peripheral nervous system and this is the least common clinical presentation of nervous system lymphoma. Most neurolymphomatosis is due to B-cell non-Hodgkin lymphoma, and most patients show lymphomatous infiltration in the meninges and brain parenchyma, in addition to peripheral nervous system involvement. We diagnosed a case of neurolymphomatosis that was confined to the right 4th and 5th lumbar nerve roots without involvement of the meninges or brain parenchyma in a patient with the nasal-type extranodal natural killer/T-cell lymphoma. We made this diagnosis based on the MRI and 18F-FDG PET-CT findings and the clinical manifestations.