Hematologic cancers including leukaemia and lymphoma have a high incidence and present tumour cells that express the antigen CD19 in their membrane. Therefore, as an alternative to conventional treatments such as chemotherapy or radiology, these cancers are being treated with Chimeric Antigen Receptor (CAR) T cells therapy, in this case CAR-CD19 (ARI-0001). However, patients treated with CAR-T therapies have shown some non-desired side effects such as cytokine release syndrome and neurotoxicity. Natural killer (NK) cells have become a promising cell source to develop CAR-engineered cell products since they exhibit an intrinsic antitumor capacity without the need for sensitization and reported no non-desired side effects like CAR-T therapies. Moreover, the absence of T-cell receptors in these cells allows the generation of allogenic off-the-shelf cell products minimizing the risk of generating graft versus host disease on infused patients. To develop this product, NK cells are usually isolated from adult peripheral blood or cord blood units. Nevertheless, these cells have shown low fold expansion in vitro, which may complicate reaching the number of cells required for the doses usually employed in CAR-based therapies. In this sense, NK cells derived from in vitro differentiation of CD34+ hematopoietic stem cells have been proved to have a high fold expansion. In this regard, we have obtained a mature and functional NK cell population derived from in vitro differentiated cord blood CD34+ cells. Besides, we overcame the challenge to implement the protocol into a GMP feeder-free system so generated NK cells could be used in CAR-NK therapies.