Manipulation of gene expression by means of microRNAs (miRNAs) is one of the emerging strategies to treat cardiovascular and cancer diseases. Nevertheless, efficient delivery of miRNAs to a specific vascular tissue is limited. In this work, a short peptide Arg-Glu-Asp-Val (REDV) was linked to trimethyl chitosan (TMC) via a bifunctional poly(ethylene glycol) (PEG) linker for the targeted delivery of microRNA-126 (miRNA-126) to vascular endothelial cells (VECs). The morphology, serum stability and cytotoxicity of the polyplex/miRNA complexes, namely, TMC/miRNA, TMC-g-PEG/miRNA and TMC-g-PEG-REDV/miRNA, were investigated along with the cellular uptake, proliferation and in vitro miRNA transfection efficiency. By REDV modification, the TMC-g-PEG-REDV/miRNA complex showed negligible cytotoxicity, increased expression of miRNA-126 and enhanced VEC proliferation compared with the TMC/miRNA and TMC-g-PEG/miRNA complexes. In particular, the approaches adopted for the miRNA delivery and targeted peptide REDV modification promote the selective uptake and the growth of VECs over vascular smooth muscle cells. It was suggested that the REDV peptide-modified TMC-g-PEG polyplex could be potentially used as a miRNA carrier in artificial blood vessels for rapid endothelialization.