This retrospective series explores temozolomide monotherapy in elderly patients with primary CNS lymphoma (PCNSL) and severe comorbidities. In 17 patients (62-90 years old), the complete response rate was 47%, median progression-free survival was 5 months, and median overall survival was 21 months. Five of 17 patients (29.4%) had prolonged responses for at least 12 months and survived for more than 24 months. Three of these patients had a methylated O(6)-methylguanine-DNA methyltransferase (MGMT) promoter, while the MGMT status was not assessable in the remaining two patients. Temozolomide monotherapy appears to be effective in a subgroup of elderly PCNSL patients and deserves further evaluation.