Post-transplant lymphoproliferative disorder (PTLD) is a serious complication after hematopoietic stem cell transplantation (HSCT). Several studies of risk factors for PTLD have been reported; however, the probability of, and risk factors for, PTLD in patients with lymphoma are unknown. Japanese nationwide transplant registry data from 5270 patients with lymphoma after allogeneic HSCT were analyzed. Mature B-cell, T/NK-cell, and T-cell lymphoblastic subtypes accounted for 49%, 26%, and 9.6% of lymphoma cases, respectively. Rituximab was used in 1678 lymphoma patients, most of whom (89%) received HSCT for mature B-cell lymphoma. Thirty-one patients with lymphoma developed PTLD, representing a probability of 0.77% at 2 years post-HSCT, which did not differ significantly from that in patients with other diseases (P = 0.98). Year of HSCT after 2010 [hazard ratio (HR) = 5.6, 95% confidence interval (CI), 1.48-21.3], anti-thymocyte globulin (ATG) use in the conditioning regimen (HR = 4.5, 95% CI, 1.61-12.5), and no rituximab use before HSCT (HR = 3.2, 95% CI, 1.26-7.90) were identified as risk factors for PTLD. Probabilities of PTLD at 1 year post-HSCT according to rituximab and ATG use were 0.23% (rituximab+, ATG-), 0.75% (rituximab-, ATG-), 1.25% (rituximab+, ATG+), and 3.53% (rituximab-, ATG+). Regarding lymphoma subtypes, patients with mature B-cell lymphoma had the lowest incidence of PTLD (0.35% at 2 years). Among high-risk patients receiving ATG, the mortality rate due to infection was elevated in those previously treated with rituximab (22%) relative to those without (14%); however, the difference was not significant (P = 0.10). Rituximab use before HSCT significantly reduces the risk of PTLD. Adding rituximab to the conditioning regimen is potentially a good strategy to prevent the development of PTLD in high-risk patients. This article is protected by copyright. All rights reserved.