Precisely delivering siRNA to its target site in cancer cells is a high-demanding but challenging task. Herein, a biomimetic magnetosome is developed using magnetic nanocluster (MNC) as the core and Arg-Gly-Asp (RGD) decorated macrophage membrane as the cloak, which is achieved via a combination of MNC synthesis, azide-membrane engineering, electrical assembly, and click chemistry. Such a feature-packed magnetosome enables us to gain the success of high-performance siRNA delivery through superior stealth effect, magnetic resonance imaging, magnetic accumulation, RGD targeting, and favorable cytoplasm trafficking. As a result, target gene expression can be significantly suppressed and tumor growth is effectively inhibited, while the systemic toxicity is not notable. These results together vote the biomimetic magnetosome as a promising siRNA delivery system for anticancer therapy.