Introduction Chimeric Antigen Receptor T (CAR T) cell therapy with axicabtagene ciloleucel and tisagenelecleucel has been approved by the United States FDA for treatment of relapsed/refractory large B cell lymphoma subtypes based on encouraging data from the ZUMA-1 and JULIET trials, respectively. However, neither of these trials included patients who had previously undergone allogeneic stem cell transplantation (alloHCT). Here, we report our experience of patients treated with CAR T cell therapy following a prior alloHCT for relapsed/ refractory B cell lymphomas. Methods/ Results Since the first FDA approval in October 2017, three patients underwent CAR T cell therapy after a prior alloHCT at our center. Details of patient, disease, alloHCT were obtained retrospectively from patient health records and are outlined in Figure 1 while details about CAR T therapy are elaborated in Figure 2. All three patients were treated for diffuse large B cell lymphoma and received axicabtagene ciloleucel at 269, 291 and 1914 days after alloHCT. T cell chimerism was 100% in one patient and 18% in another patient, while this information was not available for the third patient. At one-month post CAR T cell therapy, one patient had complete response, one had partial response, and one had progression of disease. Two patients without a complete response eventually died of progressive disease at 106 and 77 days post CAR T cell, respectively. One patient developed grade 2 cytokine release syndrome and grade 2 neurotoxicity; treated with tocilizumab and corticosteroids, respectively, with complete resolution of symptoms. This patient required intensive care unit admission for 5 days. The other 2 patients did not have any CAR T cell related adverse events. Two patients had a prior history of graft-versus-host disease (GVHD). One had prior moderate skin chronic GVHD and another had previous stage 2 gut GVHD along with possible liver GVHD (transaminitis only). GVHD had resolved at time of CAR T cell treatment, although one patient was still on immune suppression, which was discontinued prior to leukapheresis. Neither patient had worsening of GVHD symptoms or development of new symptoms related to acute or chronic GVHD following CAR T cell therapy. Conclusion Based on our series, it appears feasible to consider CAR T cell therapy treatment in patients with relapsed B cell lymphoma subtypes following an alloHCT, without concerns of worsening of GVHD. So far, there is one more report of 5 patients with DLBCL who received allogeneic gene modified T cells without worsening GVHD in these patients (Brudno et al JCO 2016). This needs to be further explored in a larger series of patients to confirm safety and efficacy of such utilization.