<b><i>Background:</i></b> Antibodies blocking the PD-1/PD-L1 axis have been shown to have substantial antitumor effects also in the treatment of Hodgkin's lymphoma (HL) relapsing after conventional chemotherapy or even autologous hematopoietic stem cell transplantation (autoHSCT). In the case of allogeneic HSCT (alloHSCT), this treatment bears the risk of inducing graft-versus-host disease (GVHD). So far, only a small number of patients who developed acute GVHD after PD-1 antibody administration are described in the literature. <b><i>Case Reports:</i></b> We herein report the cases of 2 HL patients after alloHSCT who both responded well to the therapy; however, 1 patient developed chronic GVHD (cGVHD) within 3 days of administration of nivolumab. This patient already had a history of cGVHD and interestingly showed manifestations at the very same sites. The other patient never showed any signs of cGVHD, even with the administration of 13 cycles of anti-PD-1 therapy and large doses of donor lymphocytes. <b><i>Conclusion:</i></b> The rapid reappearance of cGVHD after blockade of PD-1 implies an important role of PD-1/PD-L1 in peripheral immune tolerance in cGVHD after alloHSCT and warrants further investigation.