The CRISPR/Cas9 (clustered regularly interspaced short palindromic repeat/CRISPR-associated nuclease-9) system which adapted from the prokaryotic immune system, is the latest RNA/ protein complex to be included among genomic engineering tools. CRISPR/Cas9 technology catalyzes the formation of double-strand breaks in DNA, according to the Watson-Crick base pairing in a interested region of the genome, via endonuclease Cas9 and guide RNA (sgRNA). Genomic regulation is performed by repairing these fractures using (Homologous Recombination or HDR: Homology-Directed Repair) and (NHEJ: Non-Homologous End-Joining) DNA repair mechanisms. CRISPR/Cas9 technology is used on a wide range of platforms, starting from identification of bacterial strains, identification of gene and miRNA functions, genomic DNA fragment insertion/deletion, gene silencing, transcriptional and epigenetic targeting to creation of disease models. Leukemia, a malignancy characterized by leukocytosis in the blood/bone marrow, is caused by chromosomal rearrangements or mutations. Nowadays, genomic engineering is gaining an accelerating importance in order to elucidate the pathogenesis and molecular biology of leukemia; thus to provide more effective and personalised treatment opportunities in the future. The widely used CRISPR/Cas9 genome design technologyrepresent a new functional object for treatment of leukemia an the begining of a therapeutic new era by being applied in areas such as creation of disease models, gene insertion and silencing, epigenetic regulation. In this review, CRISPR/Cas9 technology; locus components, subtypes, stages of development of the adaptive immune response, Cas9 specificity and therapeutic gains obtained via using this technology in various types of leukemia will be discused. Also In this review, the evaluation of CRISPR/Cas9 technology in terms of ethics will be included.