A preparation of natural killer (NK) cells engineered to express a chimeric antigen receptor (CAR) specific for the tumor-associated antigens (TAAs) cluster of differentiation 19 (CD19) and CD22, with potential immunostimulating and antineoplastic activities. Upon administration, the anti-CD19/CD22 CAR-NK cells target and bind to CD19 and CD22 expressed on the surface of tumor cells. This induces selective toxicity in tumor cells expressing these TAAs. CD19 and CD22, both transmembrane phosphoglycoproteins expressed on the surface of cells in the B lineage, are often overexpressed on malignant B-cells. By simultaneously targeting two B-cell antigens, this preparation may minimize relapse due to single antigen loss in patients with B-cell malignancies.