We addressed the effect of post-transplant lymphoproliferative disorder (PTLD) treatment with rituximab monotherapy or CHOP-based chemotherapy (± rituximab) after upfront immunosuppression reduction (IR) on renal graft function in a longitudinal analysis of 58 renal transplant recipients with PTLD and 610 renal transplant controls. Changes in the estimated glomerular filtration rate over time were calculated from a total of 6933 creatinine measurements over a period of >1 year using a linear mixed model with random and fixed effects. Renal graft function significantly improved with treatment of PTLD, especially in the chemotherapy subgroup. Patients treated with IR+chemotherapy ± rituximab had a noninferior graft function compared with untreated controls suggesting that the negative impact of IR on the renal graft function can be fully compensated by the immunosuppressive effect of CHOP. The immunosuppressive effect of single agent rituximab may partially compensate the negative impact of IR on the graft function. Thus, it is possible to reduce immunosuppression when using chemotherapy to treat PTLD.