Anti-BCMA-directed chimeric antigen receptor (CAR) T cells are effective treatment for patients with refractory/relapsed multiple myeloma (RRMM). However, little is known about the impact of previous allogeneic hematopoietic stem cell transplantation (allo-HSCT) on lymphocyte collection for production of CAR T cells and subsequent treatment with CAR T cells. We performed a retrospective analysis of cellular composition of lymphocyte collections, CAR T cell expansion and treatment outcomes of RRMM patients undergoing therapy with idecabtagene vicleucel (ide-cel) with and without history of allo-HSCT. 27 patients (11/27 female) with median age 63 (range 39-75) years were analyzed. Five patients (19%) had the history of allo-HSCT median of 5.5 years before ide-cel. Prior to apheresis, the white blood cell, absolute lymphocyte counts, CD3+ cells and monocytes did not differ in patients with and without prior allo-HSCT. We also noticed no differences in the collected CD3+ yields or cellular compositions of lymphocyte collections. One year after ide-cel infusion, the progression-free survival and overall survival of patients with and without previous allo-HSCT did not differ with 60% and 45% respectively (P = .58) and 66.7% and 74% respectively (P = .84). The highest expansion of CAR T was detected between day 7 after infusion and showed no difference regarding previous allo-HSCT (P = .71). No graft-versus-host disease during the follow-up was detected. Our data confirm that the treatment with ide-cel is feasible for patients with prior allo-HSCT. Furthermore, allo-HSCT did not influence cellular composition of lymphocyte collections, clinical outcome or in vivo expansion of ide-cel. Anti-BCMA-directed chimeric antigen receptor (CAR) T cells are effective treatment for patients with refractory/relapsed multiple myeloma (RRMM). The experience regarding the impact of previous allogeneic hematopoietic stem cell transplantation (allo-HSCT) on treatment with CAR T is limited. We reported about impact of previous allo-HSCT on cellular composition of lymphocyte collections, CAR T expansion and treatment outcomes of patients with RRMM undergoing treatment with idecabtagene-autoleucel (ide-cel). The treatment with ide-cel is feasible in patients with history of allo-HSCT. We noticed no negative impact of allo-HSCT on cellular composition or outcomes of the patients.