Antibody-based immunotherapy represents a promising strategy to target and eliminate chemoresistant leukemic cells. Here, we evaluated the CD33/CD3-bispecific BiTE® antibody (AMG 330) for its suitability as therapeutic agent in AML. We first assessed CD33 expression levels by flow cytometry and found expression in >99% of patient samples (n=621). CD33 was highest expressed in AMLs with NPM1 mutations (p<0.001) and lower in AMLs with complex karyotypes and t(8;21) translocations (p<0.001). Furthermore, leukemic stem cells within the CD34(+)/CD38(-) compartment displayed CD33 at higher levels than healthy donor stem cells (p=0.047). In MS-5 feeder cell-based long-term cultures that supported the growth of primary AML blasts for up to 36 days, AMG 330 efficiently recruited and expanded residual CD3(+)/CD45RA(-)/CCR7(+) memory T-cells within the patient sample. Even at low effector to target ratios, the recruited T-cells lysed autologous blasts completely in the majority of samples and substantially in the remaining samples in a time- dependent manner. This study provides the first correlation of CD33 expression levels with AML genotype in a comprehensive analysis of adult patients. Targeting CD33 ex-vivo using AMG 330 in primary AML samples led to T-cell recruitment and expansion and remarkable antibody-mediated cytotoxicity suggesting efficient therapeutic potential in-vivo.