Background: Genistein (C 15 H 10 O 5) is a soy isoflavone with anti-cancer properties such as inhibition of cell growth, proliferation and tumor invasion, but effective dosage against hematopoietic malignant cells was not in non-toxic range. This property cause to impede its usage as chemotherapeutic agent. Therefore, this hypothesis raised that synthesizing biocompatible nanoparticle could assist to prevail this struggle. Methods: Genistein covalently attached on Fe 3 O 4 nanoparticles decorated with carboxymethylated chitosan to fabricate Fe 3 O 4-CMC-genistein in alkaline circumstance. This obtained nanoparticles were evaluated by TEM, DLS, FTIR, XRD and VSM and its anti-cancer effect by growth rate and MTT assays as well as flow cytometer on ALL cancer cell lines. Results: Different evaluations indicated that the drug delivery vehicle had a mean diameter size around 12ƞm with well bounded components. This system presented high degree of magnetization and superparamagnetic properties as well as good water solubility. In comparison with pure genistein, significant growth inhibition on hematopoietic cancer cells in lower dose of genistein nano-conjugated onto Fe 3 O 4-CMC. It increased long lasting effect of genistein in cancer cells also. Conclusion: This delivery system for genistein could be remarkably promised and futuristic as biocompatible chemotherapeutic agent against hematopoietic malignant cells.