Recently, various molecular targeted therapies have been developed for peripheral T-cell lymphoma (PTCL). However, relapsed/refractory (r/r) PTCL is associated with poor outcomes. Allogeneic stem cell transplantation (allo-SCT) can be effective against r/r PTCL owing to its graft-versus-lymphoma effect. Nevertheless, a posttransplant relapse is common. Although post-transplant preemptive therapy has shown favorable outcomes in leukemia, reports on its use for PTCL are extremely limited. We herein present the case of a patient with refractory PTCL who underwent allo-SCT followed by preemptive therapy with tucidinostat. The patient has maintained complete remission for 2-years. Thus, given its mechanism, tucidinostat may be a viable option for post-transplant therapy.