The systemic delivery of oligonucleotide therapeutics to the brain is challenging but highly desirable for the treatment of brain diseases undruggable with traditional small-molecule drugs. In this study, a set of DNA nanostructures is prepared and screened them to develop a protein corona-assisted platform for the brain delivery of oligonucleotide therapeutics. The biodistribution analysis of intravenously injected DNA nanostructures reveals that a cube-shaped DNA nanostructure (D-Cb) can penetrate the brain-blood barrier (BBB) and reach the brain tissue. The brain distribution level of D-Cb is comparable to that of other previous nanoparticles conjugated with brain-targeting ligands. Proteomic analysis of the protein corona formed on D-Cb suggests that its brain distribution is driven by endothelial receptor-targeting ligands in the protein corona, which mediate transcytosis for crossing the BBB. D-Cb is subsequently used to deliver an antisense oligonucleotide (ASO) to treat glioblastoma multiforme (GBM) in mice. While free ASO is unable to reach the brain, ASO loaded onto D-Cb is delivered efficiently to the brain tumor region, where it downregulates the target gene and exerts an anti-tumor effect on GBM. D-Cb is expected to serve as a viable platform based on protein corona formation for systemic brain delivery of oligonucleotide therapeutics.