Indolent CNS lymphomas (CNSLs) are rare and no guidelines exist for management. Recent literature highlights the potential for safe and tolerable intrathecal (IT) delivery of rituximab, a large anti-CD20 monoclonal antibody, for aggressive CNSL. We report a patient with relapsed indolent CNSL who failed systemic rituximab and could not tolerate IT chemotherapies, but had an objective response of 6 months duration to IT rituximab.