The article presents a case report of rare unclassified peripheral T-cell lymphoma (PTCL) in a child. The disease was characterized by refractory course and addition of immune checkpoint inhibitors (ICI) to chemotherapy resulted in remission induction. The rationale for immunotherapy was presence of programmed cell death ligand 1 (PDL1) on the cells of tumor microenvironment. First remission was consolidated with autologous hematopoietic stem cell transplantation (HSCT), and second remission was followed by allogeneic HSCT.Post-transplant period was complicated by severe acute graft-versus-host disease (GVHD) successfully managed with ruxolitinib. To perform local control, intrathecal cytostatic therapy was used prior to HSCT and post-transplant. Three years after last transplantation, the patient is disease-free and GVHD-free, with overall good quality of life and only mild impairment of cognitive functions.