ABSTRACTPurposeThe prognosis of relapsed primary central nervous system lymphoma remains a concern. This study aimed to compare the effects of various patient‐ and disease‐related factors on the prognosis of relapsed primary central nervous system lymphoma (PCNSL).MethodsWe retrospectively collected real‐world data from eight Finnish hospitals on 198 patients diagnosed with PCNSL between 2003 and 2020. Characteristics of the patients were available. At total of 63 patients with relapses were included after excluding seven isolated ocular relapses.ResultsThe median progression‐free survival after relapse was 3 months. The median overall survival after the first relapse (OS2) was 4 months. Patients aged 70 or younger with good performance status who received autologous stem cell transplantation (ASCT) consolidation as second‐line treatment had significantly better OS2 of 39 months (p = 0.002). OS2 for patients without ASCT consolidation remained at 3 months. Age over 70 years, poor performance status, and a first‐line progression‐free survival of less than 6 months negatively impacted the prognosis.ConclusionThis study confirms previous findings of poor outcomes in patients with relapsed PCNSL. Some subgroups, particularly those receiving ASCT consolidation, can achieve long‐term remission with current treatment options. New treatment strategies are needed for patients ineligible for ASCT or those who do not respond to salvage induction therapies.