Systemic delivery of therapeutic nucleic acids to target cells and tissues outside of the liver remains a major challenge. A biomimetic high-density lipoprotein nanoparticle (HDL NP) is synthesized for delivery of a cholesteryl-modified therapeutic nucleic acid to vascular endothelial cells (ECs), a cell type naturally targeted by HDL. HDL NPs adsorb cholesteryl-modified oligonucleotides and protect them from nuclease degradation. As proof of principle, we deliver RNAi targeting vascular endothelial growth factor receptor 2 (VEGFR2) to ECs to effectively silence target mRNA and protein expression in vitro. In addition, data show that treatment strongly attenuates in vivo neovascularization measured using a standard angiogenesis assay and in hypervascular tumor allografts where a striking reduction in tumor growth is observed. For effective delivery, HDL NPs require the expression of the cell surface protein scavenger receptor type-B1 (SR-B1). No toxicity of HDL NPs is measured in vitro or after in vivo administration. Thus, by using a biomimetic approach to nucleic acid delivery, data demonstrate that systemically administered RNAi-HDL NPs target SR-B1 expressing ECs to deliver functional anti-angiogenic RNAi as a potential treatment of cancer and other neovascular diseases.